Hi All-

As you've already deduced from the title, I'm looking into a possible cause (if any) for "meh" performance of my 2002 S (not the .5) in slow or stopped traffic on particularly hot days here in sunny California.

I have read the absolutely epic HVAC troubleshooting guide created by kr98864; a giant thank you from me for the incredible amount of information and education in that thread. To confirm... "I (G), do solemnly swear to follow all appropriate steps in this troubleshooting guide. Furthermore, I promise not to skip around and if this guide works for me, I will post useful comments to help others."

With that out of the way, here's a quick run down.

On days of lower ambient temperatures and/or night driving, my A/C performs as expected in all situations. During days of higher ambient temperatures (80 F and above), the A/C performs as expected, at speeds above 15-20 mph. (My assumption being from the ram air effect) However, at typical LA speeds (under 20mph) or stopped traffic (including temporary stops, such as a stop light), the vent temperature rises significantly (around 20-30F) in the most extreme cases (again, only on hotter days).

My testing so far...

- All of the functionality for the HVAC system tested normal using the steps in the epic guide (Including the DCCV and the microfiber towel on the grille test)
- I added about 1.5 ounces of R134a to the system (per the post recommendation and using a kitchen scale for measurement) and have not seen any improvements.
- Coolant temperatures for the engine itself never move above dead center on the gauge. (I have tested the gauge by disconnecting the fan and it did rise above the center line)
- The exterior temperature sensor is working as expected and displays the proper ambient air temperature on the HVAC controls. (I also replaced the sensor for good measure)
- Regardless, I plan to use a foam cleaner (made specifically for cleaning condensers and radiators) along with a power washer to clean the fins of the condenser. (A quick google search will present you with several videos which show how effective this can be)

Keeping this in mind, here is my question to you fine folks...

1. When your A/C is on full blast, how fast does your radiator fan spin at idle? Does it create a noticeable amount of noise?.....
If your answer is yes, your fan does in fact spin at a very high rate in hot weather, I have a few thoughts........
If the answer is no, your fan top speed is enough to move air, but does not kick into a "high gear" my thoughts are.......
Any thoughts would be greatly appreciated! Absolutely check out the epic HVAC troubleshooting thread at the link below; it is a plethora of information and if you are a complete nerd like myself, a fascinating read.

-G


https://www.jaguarforums.com/forum/s...ol-how-185002/

 

Ah, good effort at sucking up, much appreciated, but it's missing a certain je ne sais quoi. After some thought, it hit me. You've highlighted my amazing technical skills, but said nothing of my stellar personal attributes. Specifically: my modesty, good looks, and rumors that I smell nice.


That's a big jump in outlet temperature. Five degrees is within reason, but you're at least four times over that. For troubleshooting, look at the problem as a supply and demand situation. Just guessing at a number, but let's say the AC system is working at only 75% capacity, with the exact reason(s) still undetermined. Under most conditions, that 75% is plenty, as you have already observed. The supply of cool air exceeds demand, so all seems good. Adequate forward speed (plenty of ram airflow through the condenser) and high engine speed (high compressor RPM) create optimal conditions. But slowing down (less ram airflow and slow compressor RPM) suddenly decreases the supply side of the equation, and duct temperature increases. There's no reserve available for when conditions are toughest.

You were concerned about the fan operation. Duplicate the fault conditions in your driveway and watch the compressor clutch operation. See post #36 for specific symptoms you'd see if the fan was not moving enough air. If you had inadequate airflow through the condenser for any reason, the high side pressure will climb too high. The AC pressure sensor will kick in as designed and de-energize the compressor clutch. Therefore, if the clutch releases, you've likely got an airflow problem. If the clutch stays engaged, airflow is adequate and the problem is elsewhere.

Also see post #18 for details about fan belt tension. If the belt is slipping, this can reduce compressor performance. You may also notice the power steering seems heavy. See my comments about belt dressing, and how that returned performance to normal.

See post #17 for details on checking for ice accumulation on the evaporator.

After that, continue working through post #4 in the guide:

https://www.jaguarforums.com/forum/s...2/#post1714573


Specifically, be sure to check the compressor control relay, and swapping with a known-good relay if suspect. Also check the clutch for slipping, using a test jumper at the relay socket.

Do you have a test gauge set? If not, beg, borrow, or steal one and make sure the compressor can draw the low side down to approximately 29 PSI. I just noticed there's a typo in the guide for this value, which unfortunately I can't correct. I'll have to add a note to the thread.

If the compressor can't pull down to 29PSI, please be aware this may not be the fault of the compressor itself. It could be a problem with a slipping drive belt, slipping clutch, or reduced voltage to the clutch coil. Don't just automatically condemn the compressor.

If everything in post #4 checks good, your car would be a good candidate for the compressor modification as detailed in the guide. Before changing any parts, I'd strongly consider doing a full evacuation and recharge. And if doing that, you can do the compressor mod at the same time.

 

Do you smell like rich mahogany? (Name that movie) If so, I'm impressed. But in all seriousness, thank you for your continued help. I geek out on this stuff, even if I do not have any issues to fix.

Here's where we are at.

Had the S in for an oil change this morning and asked if their A/C technician was in the shop; he was and we had a chat.

Fun backstory, the dealership I go to religiously is a Ford dealership since my DD is an Expedition. (If you think I'm crazy, I'll explain why everyone should do this) Every time I pull into the service driveway with the S, the techs and service advisors stop and stare with an admiring but confused look on their faces. (i.e. What's THAT doing here??) As soon as I explain it's a Duratec V6 with a Jaguar intake on it and a 5R55N transmission, they all go "ooohhhhhhhhhhh, yeah we can work with that, no problem".

After a quick LOF, I headed into the shop and picked the A/C technicians brain a bit. I explained some of the poor performance I'm troubleshooting and he was interested enough to have me explain how the system works (with many direct quotes and kudos given to you KR).

Once I pointed out the low and high side ports, he suggested I do a complete evacuation and recharge, since I have no idea when (or if) it had ever been done. He let me shadow him while he hooked up the gauges and machine (and was nice enough not to charge me any labor, since we taught each other a few things).

First jackpot found when he first attached the gauges; a slow leak on the low side port schrader valve. Luckily they had one in stock; replaced and recharged system. We both checked vent temps and found them to be between 42-50F steadily, which I was pleased with.

During my drive home, I noticed the vent temps dropped while I was above 15mph (attributing that to the ram air effect); but were slightly warmer at stop lights and in traffic (still within the acceptable range)

Now here's where it gets interesting...during testing, I found that the driver side vents are always slightly cooler than the passenger side vents, but again, only at a stop. Once in motion, everything is gravy. It's not a huge difference, maybe 7-8 degrees. But I immediately thought back to the DCCV and pondered if the passenger side valve isn't closing all the way.

For good measure, I cycled from "LO" to "HOT" a couple times, no change.

So to put it in KR's words, the system is definitely "making cold", the question now is there a small amount of heat being dumped into the passenger side vents where it's enough to slightly warm the air when stopped.

I've read the walkthrough on replacing the DCCV...it's doable, just messy. (I'm a apartment-parking-garage-with-ramps type of mechanic) I had a couple thoughts to start with, but please yell "STOP" if they are dumb or dangerous. I won't be touching anything until I get your opinion.

1. Just leave it. It's a minimal difference that only I notice. The Type A in me has a BIG problem with this and will bug the hell out of me. But if the proper answer is to leave it, so be it.

2. Giving a GENTLE couple taps on the DCCV valve to see if I can free up a sticky point somewhere on the passenger side valve. (Again, feel free to yell STOP at anytime)

3. After reading the replacement thread, I saw the teardown of the old valve. I wonder if it would be possible to remove the top cover and pull the actuators out, without having to remove the entire DCCV. Give those a little lubrication and manually move the valves up and down a few times to make sure they move freely. The idea here would be to avoid having to pull the entire DCCV out and on top of that, replace the lost coolant and perform an air bleed.

I mentioned the Jaguar approved modification to the technician while we were doing the evacuation and refill, but he wasn't up for that, which I totally understand. (If they break something, it would be on them) If it comes down to it, I can find a specialist here or even go to the Jag dealership and ask them nicely.

Any thoughts as the saga continues?

-G

 

LLLA: I too take my S-type to a Ford agency. I live in a small town in Eastern Montana and there are NO Jaguar dealerships in the state, or Wyoming either for that matter. I was originally from Kalifornia and moved to Montana a couple of years ago; in my case, I actually asked the service manager at the local Ford dealer if they would work on the car prior to purchasing my S-type. Once I explained what the car actually was (the Lincoln LS and Thunderbird's British cousin) the service manager said "sure". I just had my S-type in for a re-charge of the A/C as well; it was making cool, but not cold. No leaks found and the system is now squared away...

 

Well, that escalated quickly...

42 is okay stationary, but 50 is still a bit high. Were these values recorded while parked?


Ram air may not be the primary factor. Engine RPM and thus compressor speed will be higher when moving faster. So if there's something limiting compressor performance (slipping clutch, for example), increased RPM may be masking the root cause.

7 or 8 degrees is a big difference. Something ain't right. Are you running these tests in manual LO? That will override most (but not all) of the automatic control inputs. For now, make sure you test in manual LO so we can differentiate between a cooling problem or a bad input from the automatic control system.

Have you tested the DCCV as described in post #2 in the troubleshooting guide? You already have a thermometer handy, as you've been recording duct temperatures. Just for giggles, I verified the operation of the DCCV on my '02 this morning on the way to work. Manual LO selected. AC switched off (very important). Fan on medium speed. Ambient temperature 65F. A favorite song playing on the stereo, a VERY important factor:



Duct temperature on both sides was 67F. That confirms the DCCV is not letting hot coolant reach the heater core when commanded off.

I suspect your DCCV will fail this test.

In the guide, you will also see a troubleshooting recommendation to pinch off the heater core return line. If the duct temps drop, that means the DCCV was letting hot coolant reach the heater core.


Been there, done that, got the T-shirt. Made no difference.


Your call. Myself, if I'm going to have AC, I want to be able to smuggle penguins in the middle of summer and have them complain they're cold.

Heck, try a jackhammer. Doubt it will make any improvement.

Oh, you mean like in post #42 in the guide? An in situ replacement of the innards is not difficult. I don't think lubrication is going to help. Coolant is already slippery stuff. Most likely you will find the seals swollen or otherwise jammed.

https://www.jaguarforums.com/forum/s...repair-251854/

In addition to the potential DCCV issue, I think you've got something limiting compressor performance. Have you tested the clutch for slippage? Have you tried swapping the clutch relay?

 

+1 on Karl's excellent advice!

Another thing to check, if you haven't done so already, is the serpentine belt condition and tension. There is a wear indicator on the tensioner that shows when the belt is stretched beyond it's service design and should be replaced. If the belt is slipping slightly at idle when the compressor cycles on and off, it can affect refrigerant flow to the evaporator.

 

Back for more!

Note: The tests I did this evening did NOT include a thermometer. I had just come home from work and wanted to check a couple things because it was bugging me. (I know, not proper procedure. I will use thermometer tomorrow)

Setting
S has been sitting all day in the garage, ambient temperature is approx. 74 degrees. All of these things were checked with setting on LO

- With A/C on LO, vent temps felt proper (nice and chilly) to me. (Will give you the real number tomorrow)

- With A/C on LO, compressor is engaged continuously and does not cycle on and off. (At least for the 10 minutes I was doing my testing)

- Swapped Fog Lamp relay with compressor relay. I want to say this made a difference because it looks like the compressor was spinning faster, but I could totally be full of it. Plus the relay worked fine for the fog lights.

- When I first started, I felt the two cabin intake lines on the DCCV with my hand. Both felt cool and the same temperature. After 10 minutes or so of idling, both lines continued to feel cool and the same temperature. The return line felt hot. (Yes I know, will check with actual readings tomorrow for you)

- With A/C on LO, fan spins continuously. I managed to get a video of it in action. This might be totally useless, but I figured I would try. To me, the fan is spinning slower than what I would expect a cooling fan to spin when calling for full A/C; almost leisurely to me. But, I could be totally wrong; hoping you might be able to tell from the video. Also probably worth noting the speed you see there is THE fan speed. Never goes faster or slower and the engine is always louder than the fan. (Unlike cars you hear idling in the parking lot where the fan kicks into super turbo high gear occasionally)


More to come tomorrow when I test with the proper tools.

-G

 

Who likes data? I like data. Let's review some data.

TL-DR
1. DCCV appears to be operating normally. I did not observe any major differences in temperatures both from the driver/passenger vents (both during the unloaded and loaded tests), nor did I see any major differences in temperatures on the cabin intake lines coming off the DCCV. I'm attributing the minor and gradual increases in temps from the DCCV to engine bay heat (correct me if that's wrong).

1.5 Ambient air temperature during testing was 77

2. The coldest air at start idle (before rising the engine RPM) - Driver: 60 and Passenger: 62

3. The coldest air at 2000 RPM - Driver: 39 Passenger: 37

4. The coldest air of test, engine RPM at 2800 RPM - Driver: 36 and Passenger: 35

5. Return to idle vent temps stabilized at - Driver: 56 and Passenger: 57


All temperatures are in Fahrenheit and system was in LO the entire time (EXCEPT during first ambient air test were A/C switch was specifically off to test vent temp differences) Time is in minute increments (HH:MM)


0:00 - Engine Off

0:01
Starting Ambient Temp (per car HVAC sensor): 77
This aligns with current outside temperature.

0:01
DCCV Cabin Intake Line A: 79
DCCV Cabin Intake Line B: 79
DCCV Return Line: 79

0:02 - Engine Start - HVAC Set to LO - A/C OFF

0:02
DCCV Cabin Intake Line A: 80
DCCV Cabin Intake Line B: 80
DCCV Return Line: 80

Vent - Driver: 80
Vent - Passenger: 80

0:05
DCCV Cabin Intake Line A: 89
DCCV Cabin Intake Line B: 84
DCCV Return Line: 90

Vent - Driver: 82
Vent - Passenger: 83

0:08
DCCV Cabin Intake Line A: 90
DCCV Cabin Intake Line B: 90
DCCV Return Line: 106

Vent - Driver: 81
Vent - Passenger: 82

0:10
DCCV Cabin Intake Line A: 94
DCCV Cabin Intake Line B: 91
DCCV Return Line: 114

Vent - Driver: 82
Vent - Passenger: 82

0:11 - Engine Idle Speed - HVAC Set to LO - A/C ON

From here on, I measure vent temps only

0:14
Vent - Driver: 62
Vent - Passenger: 64

0:20
Vent - Driver: 60
Vent - Passenger: 62

0:21 - Hold Engine at 2000 RPM

0:22
Vent - Driver: 51
Vent - Passenger: 52

0:24
Vent - Driver: 44
Vent - Passenger: 44

0:26
Vent - Driver: 39
Vent - Passenger: 37

0:27 Hold Engine at 2800 RPM (Limiter)

0:28
Vent - Driver: 36
Vent - Passenger: 36

0:30
Vent - Driver: 36
Vent - Passenger: 35

0:31 Return Engine Rev to Idle

0:32
Vent - Driver: 53
Vent - Passenger: 55

0:36
Vent - Driver: 56
Vent - Passenger: 56

End Test


Okay so, knowing all this, here are my thoughts....

1. Does the radiator cooling fan speed change with engine RPM? I'm assuming it does not, as it is electric.

2. Assuming the engine RPM does not affect the cooling fan speed, my finger is now pointing at the compressor.

3. Assuming the R134a amounts are correct (as it was just evacuated and serviced 3 days ago)...I'm thinking first, I find a technician who will perform the TSB on the compressor valve for me. Then if that doesn't work, replace the compressor.

Now being a dark colored car, being parked out in the sun for a day and then testing I'm sure would skew the numbers. Thankfully, I do not ever have to park outside. But I would absolutely say the temps rise when driving sunlight.

-G

 

The values you recorded for the heater hoses look good, and would seem to indicate the DCCV is closing properly. However, that is a test I devised and perhaps it's not 100% foolproof. Maybe you've discovered some scenario where the test passes but somehow hot coolant still reaches the heater core. Some of your previous observations, specifically the side-to-side temperature split, would seemingly point to a DCCV problem. From years of troubleshooting experience, I've learned the hard way to always question my own methods when the results don't make sense. If you were to clamp off the heater return line, and positively stop any coolant flow through the heater core, you could conclusively rule out trouble with the DCCV.


IIRC, the fan speed is automatically adjusted to maintain the desired refrigerant pressure range on the high side. I don't believe it follows a schedule based on engine RPM.



Before you go for the most expensive component in the system, I've been authorized to break out the forum tranquilizer gun. Trust me, it's for your own good. Don't pull out the dart. This video explains how the process works:


Some people have said it's not safe to be shooting tranquilizer darts at other forum members. I have to respectfully disagree. I know to keep the safety engaged until within range and ready to fire. Keep the barrel pointed away from myself at all times. Anticipate the kickback from the gun, etc. By following these basic safety rules, I should be perfectly safe.

Still determined to skip that boring troubleshooting and jump way ahead to replacing the compressor? If so, first consider getting a good book on gardening. Learn all about soil pH, fertilizers, etc. That way, you can make sure your money tree is healthy and produces copious amounts of cash.

Myself, I've got no green thumb so have to spend my money judiciously.

As previously suggested, check the serpentine belt tension, post #18 here:

https://www.jaguarforums.com/forum/s...2/#post1934020



If good, try some belt conditioner. Here's one example, approved for use on serpentine belts:

https://www.crcindustries.com/produc...7-5-wt-oz.html





After that, do the paint dot test for clutch slippage. Details in the troubleshooting guide, near the end of post #4:

https://www.jaguarforums.com/forum/s...2/#post1714573


So far, these steps will cost you about $12, for a can of belt dressing and some paint (nail polish would work and has a convenient little brush). For the jumper wire, use a paper clip that you can steal from the office for free.

Only after doing these tests (and pinching off the heater return line) would I consider the compressor. Even then, I'd be hesitant. Don't just march into a shop and ask for the compressor to be replaced. If that doesn't fix it, they only did what you said so there's no guarantee. Describe the symptoms to them, ask about the compressor mod (show them the bulletin from Jaguar), and let them decide how to proceed. Before committing to any work, ask who foots the bill if work performed doesn't fix the issue. Unless your money tree is in full bloom...

 

Three letters….TSB.

More specifically, this TSB here. After completing, there’s NO comparison. I’m getting 38F vent temps in stopped traffic at 90F ambient.

For the record, the steps above for isolating the problem(s) are 1000% correct. Treat that epic troubleshooting thread as the holy hvac gospel according to KR98664.

I went out of order on a hunch…and it worked. This does NOT give you permission to skip the steps. My fix here may do nothing for you. That said, it likely is worth doing regardless, considering there’s an OEM TSB.

——

Thursday I was furious; not at the S, but my truck. Driving on the 5 on my way home out of nowhere, the front blower motor just dies. Straight up dead in the water. Rear blower worked perfectly. Checked relays, fuses, nothing. So it’s summer, my truck has no A/C (in the front) and in traffic, the S is basically an oscillating fan. Joy….because this is how my life works.

Yesterday I take the truck to the dealership* with a few punch list items I wanted to do. “Here, take it, long as you need, here’s the CarMax warranty, call me when it’s done”. (Having two cars is a life changer) For the remainder of the day, I’m running around in the S sweating. Thus today, I was determined to get this solved or at the very least get the TSB done, to rule it out of the equation.

Despite having the TSB .pdf printed in hand, explaining the entire purpose and a personal step by step walkthrough, only one shop took me seriously. First stop was the dealership (since they did the recharge last weekend and knowing they have my truck, I was hoping they would help me). Nope, they told me to take a left. Next I called around 5 different shops and visited two in person. The other 6 either didn’t answer or told me off. Number 7 was a godsend.

Finally I stop at a small 3 bay shop, with only 2 guys.** Had good yelp reviews and I was determined to figure this out.

This guy stopped his work, listened to my explanation and throughly reviewed the paperwork. He was a bit skeptical, but willing to listen. Given the oddity of the task, I asked if we could do it together. He was happy to oblige.

——

Here’s a layman terms version of the TSB so you know what to expect. Getting to the valve without removing the compressor sucks. It can be done, but you’ll need patience and have an array of socket extenders with ratcheting wrenches. You’ll be doing this work blind, keep that in mind.

Evacuate the system, raise car on lift. A lift is essentially required, doing this on ramps would be almost impossible.

On the lift, with your body facing the front of the car, look with your flashlight and you’ll see the plate/cover mentioned in the TSB on the backside of the compressor (the plate/cover faces the rear of the car). Remove the two bolts.

You’ll need a pick to remove the valve and spring. The valve comes out first, followed by the spring. Note the orientation of the valve (flat surface faces the rear of the car; the valve will be reinstalled in the same direction)

Reverse the order. Place the valve into the compressor first, in the same orientation it came out. Then install the spring and replace the cover. The spring will now sit between the valve plate/cover and the flat side of the valve; pushing the valve toward the front of the car. Replace the plate/cover and two bolts.

Recharge the system; ensure you have a solid and consistent vacuum.

The 1999-2002 (pre-facelift) takes 0.800kg of r134a refrigerant. The 2002.5-2008 takes 0.750kg of r134a refrigerant. Ensure you are using the correct amount for your model year, as not all databases properly differentiate between the two.

Perform your standard post recharge checks, verify compressor operation and vent temps.

——

*Typically, I encourage the dealership for service, as they have a large stock and network of parts, several technicians for reference, access to all industry standard tools/databases and a genuine interest in keeping you a happy customer. Dealerships do not make money selling new cars; some is made on used cars, but the majority of revenue comes from the service department. If you show loyalty when they pull up your service history, you will undoubtedly have a better experience, get priority treatment and help when you need it. (I.e. I’m 50 miles over my warranty and this broke, can you help?) Trust me, I’ve done work for a Ford dealership before, this is how it works.

**For boutique needs such as this, most dealerships and larger shops won’t go near this stuff. Even after explaining it is made by Ford, most do not want to risk breaking something. Find yourself a small local mechanic with good reviews, who will listen to your ask and read the TSB printout. Walkthrough the ask and steps together. If you feel savvy enough, ask to shadow the mechanic during the work. (If nothing else, for educations’ sake)

This goes for anything; be a good customer. Be patient, flexible, informed, but not a know it all. Ask, do not demand; suggest, do not insist. Do not walk into a shop, slam the TSB on the counter and demand a quote. Bring cash and TIP; these folks work for a living and this type of mechanic is worth the weight in gold. Keep in mind they are doing you a favor here, as most places go out of their way to avoid this type work, no matter how much money you have. This is not a difficult job, but it is odd for those not familiar with Jaguar. Remember, they still are accepting a risk; if they break something in the process of attempting to do the work, they have eat the cost to fix it. Respect their expertise; mechanics aren’t perfect either. Sometimes you might disagree and that’s okay, as long as you are professional and respectful. No matter who you are working with, these qualities go a long way.

I was once told “it’s nice, to be nice, to the nice”. This proves true every single day.

 

Great news! Glad to hear you got it sorted out.

I've often wondered about the back story behind that compressor modification. The same basic Visteon brand compressor was used on multiple vehicles of that era. Best I can determine, Jaguar was the only company to recommend that modification.

And stop/go driving in 90F weather certainly isn't some radical extreme. The original variable output design should have been adequate. Or was this particular compressor marginal for a relatively large car? Was Jaguar getting lots of warranty claims and Visteon was stonewalling them? If the original design was adequate, a new compressor would have been an effective fix but most likely somebody got tired of eating all those claims, whether Jaguar or Visteon. And thus the modification was born.

Pure conjecture on my part, but that's my story and I'm sticking to it...

 

I agree. If the compressor is a white label part used across several makes/models, one would think a design flaw would be systemic across every use case. Perhaps Visteon’s engineering lab was different than the Jaguar system, but had specs which were “close enough” to make it fit?

$20 bucks says you’re on the money. The TSB states “…this may be due to a degradation of control valve operation, preventing the system from delivering full function potential”.

The lawyer in me reads that as “…we’ve seen an influx of warranty claims against these compressors for inadequate performance. Visteon says their compressor is working as designed and the problem is with our Jaguar overall system design. To keep customers happy and avoid issuing a recall, perform this modification”

With the TSB being issued in 2010, a guess would be as the compressor ages, the system gradually loses it’s ability to overcome the force of the spring and completely open the valve at lower RPMs. This might be due to the specific layout/design of the Jaguar A/C system, versus other designs where this doesn’t occur. Who knows, could be something simple, such as when the drive belt ages, it cannot provide enough power at idle to fully compress the spring and open the valve due to Jaguar’s belt routing. (These are total guesses; do not use this as an excuse to start throwing parts at the system)

Looking at the pictures from the X thread, the remanufactured version of the same compressor removes the valve system completely, leaving an empty space where the valve and spring would have been installed. I wonder if this was just for Jaguar or if Visteon made this change for all of these compressor models after the fact.

Also, the recharge done last weekend may have been done incorrectly. They replaced the low side schrader valve, verified that today. But perhaps they may not have used the proper amount of refrigerant. As you taught me (greatly appreciated), r134a pressures mean nothing in regards to refrigerant amounts in the system. The only true way to know is a full evacuation and recharge with the proper amount.

Considering the amount of knowledge we have now (99% thanks to you K), maybe we should start a consulting firm on vintage Jaguar HVAC systems and teach mechanics how to troubleshoot and repair them properly. No joke, something I have pondered is could one redesign the DCCV to be more reliable and compatible with the existing system.

———

Funny thought…as a kid, I always imagined these mega corporations with huge medical-style labs, white boards with complex algebra equations, giant server farms with hundreds of engineers and doctors wearing white lab coats working tirelessly to make the perfect product.

When in reality, sometime back in 2010, a middle manager somewhere at a grade B office in suburbia, was sitting in a plush leather chair at his oak desk reviewing an Excel sheet showing a spike in warranty repair costs on certain A/C systems. Wearing his white shirt and Jerry Garcia tie, he grabbed his “#1 Dad” coffee mug and walked downstairs to a small garage with a couple guys and some work benches. He just got off a conference call where Visteon said it’s not their problem and told the engineer to figure out a cheap solution by Friday. The engineer plays around with the compressor for a week, comes back upstairs into the office with his greasy overalls and hands the manager a dirty white piece of paper with a print out with steps on how to do this TSB.

 

Well as a potential downside to the compressor modification I offer up this story.

I replaced the AC compressor in my 2006 S type R about a year or so ago but before I put the new compressor in I did the mod because I didn’t wanna have to take it out a second time. and the first time the weather got up into the 90s the belt started slipping on the compressor pulley when I was really taxing the system. So yes my air conditioning is extremely cold however I have a belt slipping.

I’m about to change the belt and tensioner to try to solve the problem of having my belt slip during this heat wave that we are currently experiencing

 

Just noticed something peculiar. On the S-Type, the compressor spring modification is only applicable to 3.0 V6 models only. I wonder why that is?

I compared V6 and V8 compressors on Rockauto. They looked nearly identical, with the pulley sticking out a little bit further on V6 models. The compressor body looked to be the same, but who knows. Whatever the difference may be, it seems odd the TSB is not applicable to V8 models. The condenser, evaporator, and expansion valve were the same part numbers for both models.

 

It is my understanding that the compressors are the same apart from the length of the mounting lugs that the bolts pass through, see pic thanks to joycesjag. Also some models of compressor have had this
valve completely deleted. Second pic.






IIRC Brutal confirmed that this mod was equally effective on V8s as well as V6s.

 

Well like I said I did the mod on my S type R and it blows wicked cold at idle. But I get a belt slip when im really putting it to work in extreme heat. Once I change the belt and tensioner ill report back to say if they fixed the slip. Its way to hot to do it now.

 

See now that’s interesting. OEMs do not create TSBs forever, at some point based on the number of complaints and the age of the MY, they stop reviewing new complaints (unless it’s a safety concern like the Takata airbag disaster)

A guess would be that the V6 model is more popular, thus leading to an increased number of customer complaints specific to the 3.0. This didn’t pop on both the V6 and the V8, as they have different part numbers to fit the engine blocks, despite being effectively the same part.

Another guess would be the V8 has enough “idle horsepower” to drive the compressor and compress the spring for a longer period of time. As the system ages it becomes susceptible to the same problem, but it takes longer to show up as a concern.

Have no way to say if any of this is correct, just honest guesses based on typical OEM behavior and the experience I had (higher RPMs on the V6 = better cooling performance) I have tested my system and do not see any signs of belt slippage. However, the belt will be replaced soon anyway for good measure.

Regardless, someone knew something because the reman version of the compressor just deletes the spring/valve mechanism entirely. If someone brought in a V8 and had a similar concern, with no TSB for the V8s, the dealer likely just replaced the compressor which in turn, deleted the valve/spring mechanism. Typical Mr. John “Not-a-Mechanic” Smith is happy because his air is cold again.

 

I suspect you are correct and I was thinking the exact same thing when I modified my compressor on my STR. Also interesting is that the “new” compressor I installed recently still had the valve. It was made by Murray I believe and its not a reman. Its quite possible in my case, that Murray may have fixed the inherent problem with low speed cooling using a different spring or changing the way it cools at idle so the mod wasnt needed on this new compressor. But if you’ve ever replaced an air-conditioning compressor on an S type R you know how horrible it is trying to reach in from the back of the motor from underneath the car with all the lines and power steering rack in the way so I didn’t wanna have to take this thing out a second time and that’s why I made the modification on the bench prior to installing the compressor. So my belt slippage might be due to overworking a possibly modified and corrected compressor design. It’s too bad these things aren’t documented better either from Jaguar or aftermarket manufacturers.

 

Once in a great while i get the marginal cooling at idle and very low rpms. I found that a quick into neutral at a stop and a quick blast of throttle puts it in ice cube mode and it stays like that for a long time. I think aarcuda is right about the spring being too stiff. I always leave the ac in low mode and adjust the fan speed for less cooling anytime the ac is active for anything but heat. Then i will use the auto temp setting

 

A final note; after doing the TSB, the A/C is ICE cold at any speed or ambient temperature. Sitting in traffic at 98F outside, I actually had to turn it DOWN. Wasn’t even on MAX A/C either, that was just in automatic mode.

Thank you all for your help! Karl, I owe you.

-G