MI have been trying to solve the cooling problem on 2008 S-Type, 3.0, for about two years with no luck. I'm also reading KR98664's wonderful "Troubleshooting Guide for Climate Control" for clues and actually reading it a second time, as I wait to purchase an Infared Thermometer to measure the top hose temp and heater hoses. But I don't think the DCCV is stuck open, as I took a reading with Digital Multimeter that also has a temp probe.

But the behavior is that I run at a rock-solid 60 degrees in the cabin at idle and speeds below 1500 RPM, or in words, on city streets. As soon as I get on the interstate and get above 1500 RPM, the system starts cooling and will get down to around 40 degrees. As soon as I exit the Interstate and drive a slower speeds the cabin temp inches back up. So I'm guessing the ram-effect of air passing through the condenser at high speeds enhances the cooling. I clean out the condenser on the weekend with my air compressor and a special-order long nozzle to reach down in the tight space between the radiator and condenser. But didn't find much debris.

So I'm beginning to suspect the electric cooling fan is not operating efficiently, especially at low RPM. But the suction is strong to hold a paper towel on the grille at idle. One question I have is whether the cooling fan is supposed to run for a couple of minutes after shutting off the engine on these cars. Mine does not.. Or maybe the Jaguar is too sophisticated for such a low-class task of running the fan after you turn the engine off. I'm also trying to figure out how to test the voltage at the fan; maybe there is a voltage drop affecting the performance of the fan.

Also, does the speed of the compressor increase with engine speed? As far as I can tell, the compressor clutch does engage, but it's really hard to see everything from above looking down into the area where the compressor is located. I'll check again tonight with a flashlight.

Overall, something is out of whack with my cooling system and it's related to the engine speed and also the outside temperature, as it cools better when the outside temp is a little cooler, maybe in the 70s-80s instead of the 90s.

Thanks in advance for any insight and I'll keep studying and troubleshooting. the meantime, it looks like another hot summer.

Earnest

 

Just a disclaimer right up front.. I don't know enough about the S-Type climate control system to give a definitive answer.

If the doors are vacuum operated.. you might check for a vacuum leak. (engine load = less vacuum given to HVAC)

Yes compressor speed is linear to engine speed.

 

That sounds very much like the engine cooling fan(s) is/are not running properly or perhaps not at all.

If checking, do not put fingers or any clothing near them - very dangerous!!

 

Thanks, Jag V8. I too suspect the cooling fan might be causing my problems. I’ll check the Cooling Fan Relay (F13) after work for proper operation and also see if the fan turns on after reaching operating temperature. I guess the electrical connector for the cooling fan is buried somewhere low in the engine bay south of China.

Earnest

 

Yours may like mine have more than one fuse so be sure to check it/them, too.

 

Earnest,

Glad to hear the troubleshooting guide has been helpful to you. Please continue working through it systematically. Don't make any assumptions (Danger! Danger!) about the source of the problem. In other words, don't steer your troubleshooting efforts to match any hunches you may have. Work through the guide based on the symptoms that are present, not what you think it may be.

Please confirm you have have put the system in manual mode, with LO displayed on the control panel. This bypasses most (but not all) of the automatic functions, and is a great help for troubleshooting.

Also, please don't get fixated that poor AC performance at low vehicle speed and low engine RPM is exclusively a cooling fan issue. You've already mentioned adequate airflow at the grill at idle, with strong enough suction to hold a paper towel.

The way I'd look at is when you slow down, with low RPM and low ram airflow, that is the toughest conditions for the AC system. Freeway speeds with higher RPM? Piece of cake, because the compressor is spinning faster and you've got a virtually limitless supply of cooling air through the condenser. So if the AC system is performing marginally, it's going to act up just as you've described. Low refrigerant, a slipping drive belt, a slipping compressor clutch, etc. are all issues that would cause the same symptoms.

Consider this illustration. I, a cranky old man, went hiking with my children recently. They are all in their 20s, strong and full of vim and vigor. On the uphill portions of the hike, my performance dropped way off as they clambered ahead at full speed. I think they were secretly debating if they'd have to carry my body off the mountain, or could just get my car keys and cover me up with rocks. But on a gentle downgrade, when conditions were easiest, I kept right up with them. Watching my downhill performance, you'd have never known I wasn't operating at full capacity. Your AC system is the same way. Less than full performance won't be noticeable under optimal conditions on the freeway.

With that in mind, and after you confirm the AC system was operating in manual mode, please work through the steps in post #4 of the t/s guide. I wish I had access to edit the guide, as maybe I'd suggest checking the refrigerant level after doing some of the other easier checks. Make sure the compressor clutch relay is good. Maker sure the clutch isn't slipping, via the paint mark test. Check the belt tension, etc. Also see posts #17 and #18 for addendums.

 

Are the HVAC doors vacuum operated? (this is a common concern on fords. Slow speed vs high speed HVAC temp differences)

 

All of the HVAC doors are electrically operated.

 

Ah... thank you sir!

 

Hello KR98664,

Yes, your climate control guide has been very helpful in working toward a solution for my cooling issues. And I can confirm that I have been running in LO and manual mode for the past several months and certainly for all troubleshooting steps.

I’m doing a second read on the guidebook and making notes along the way. I also took a special interest in the “AC Pressure Sensor” you mentioned after learning it can shutdown the compressor if the high-side pressure gets too high. If I possibly have a malfunctioning cooling fan, that scenario might be a possibility. But I won’t jump ahead : )

i have about a 20 minute commute from the office and will check to see if the cooling fan is running when I get in the driveway, as the engine will be at full operating temperature.

Also plan to check all AC-related Relays and Fuses. Will report back to the forum.

Thanks again and stay tuned.

Earnest

 

Forgot to mention: Also do the test of the DCCV. If not shutting off completely, it may be dumping heat into the cabin. On the freeway, under optimal conditions, the AC system may make enough cold air that you don't notice this unwanted heat. But once you slow down, and the AC performance drops off (normal to some extent), there may not be enough margin of cold air over hot.

 

I'm back after an evening of testing and observing the operation of my climate control system and didn't find anything malfunctioning that could be the cause of my cooling issues. I can confirm the following:

The engine fan is working. Although it's very difficult to see the actual fan through the shroud and supports, I was able to observe it spinning while idling and could see the blades spinning down to a complete stop after turning engine off. As a further "suction test and air flow test," it had already passed the paper towel test of placing it on the front grille with the engine running and being held in place, but I also put heavier cloth towel directly on the front of the condenser with engine running and it also stayed in place. So the cooling fan is providing a good, strong airflow across the condenser and radiator.

All fuses and relays related to the climate control system checked out to be fine:

Relay F13: Cooling fan - OK
Fuse F32: Air Compressor Clutch, Auxiliary Coolant Pump - OK
Fuse F14: Climate Control System - OK

Although I did find it interesting that Fuse F32 has power, even with the engine off, as well for Fuse F33, adjacent to Fuse F32, for the Engine Control Module and Transmission Control Module. Maybe there are other fuses as well with constant voltage. Or is this an area of concern?

All the while, my duct temperature remained at a solid 60 degrees with the engine idling.

So I'll dig deeper. An Infrared Thermometer is on the way from Amazon to check the operation of the DCCV. And I'll check whether the clutch is slipping on the compressor. By the way, does anyone know the "air gap" specifications between the magnetic clutch and the compressor pulley?

Just a little "climate control Woes" history on this car. The DCCV has been troublesome before with the exact same symptoms of not cooling and was replaced in 2013 by a local Jag mechanic. He also said I had a short in the AC panel. Two months later I went to the local dealer with the same symptoms and they replaced the ACCM (behind the glove compartment) to the tune of around $2,000. Ouch! I'm not compelled to go that route again.

I'll enjoy cool air on the freeway today, or at least until I exit onto city streets and stop at red lights.

 

In case you find you need to replace the module they're quite cheap used and you can even get them upgraded.

 

Don't make me break out the forum's tranquilizer dart gun. Oh sure, it's fun to fire it, but those darts are expensive.

You can quickly rule out the AC pressure sensor in your situation. With the car parked, engine at idle, and AC to manual LO, watch the face of the compressor pulley. If the pulley face is spinning, that means the compressor has been commanded to engage. Even if the resulting cooling performance is poor, if the compressor clutch is engaged, that means it has received the proper signal to run the compressor. The fault would be elsewhere.

 

No problem there. Some fuses have direct battery power. There's typically a relay downstream that switches the circuit on and off.



While you are waiting, please see post #2 in the troubleshooting guide. I've listed two ways to check the DCCV. The first one only requires monitoring a thermometer in the dash vent while you go for a test drive. Follow the steps exactly as given to turn off the AC compressor and command the DCCV fully closed. If the vent temperature is significantly higher than ambient, your DCCV is not fully closed when it should be.




I don't know the air gap specs. However, I'd first check for a slipping clutch with the paint mark test. If the paint marks stay aligned, the air gap is probably okay. The only time you'd need to worry about the air gap is if the paint marks indicated slippage.




Even though you've already had the DCCV replaced, do NOT assume it is good. These poor things have a very high failure rate. Please check the operation as previously suggested. Also, please check the DCCV connector for corrosion. See new posts #20 and #21 at the troubleshooting guide for more details and some pictures:

https://www.jaguarforums.com/forum/s...2/#post2077011

 

Any update? The suspense is killing me!

 

As I continue my troubleshooting for my cooling issues, I did the "quick test" on the possibility of hot coolant getting past the DCCV and into the cabin, while I wait on an Infrared Thermometer to arrive by mail order..

To accomplish this, I followed "KR98664's" climate guide to record the ambient external temperature and the duct temperature inside the cabin with the AC off. His theory is that the two temperatures should be about the same, with no cooling assistance from the climate control system. Here is what I found during a short drive:

Outside or external temperature: 85 degrees
Left Center Duct in the Cabin: 80

When I tested the right center duct, the external temperature has gotten hotter and the inside of cabin has gotten warmer while parked for a few minutes. So these numbers are skewed a little:

Outside or external temperature: 90 degrees
Right Center Duct in the Cabin: 95

So the heater hose for the right duct might be allowing a little hot coolant to get past the DCCV and mix with the cool air coming into the cabin. I'll be able to perform a more accurate test on Monday by checking the top radiator hose and the heater hoses with an Infrared Thermometer.

Stay tuned.

Earnest

 

Hmm, those test results are inconclusive. With the AC switched off, I'm not sure how the one side is showing cooler than ambient. Maybe that's caused by the limitation in accuracy of the two thermometers. Meanwhile, the other side was reading warmer, but the ambient temperature had also climbed. You should be able to test both sides on the same trip. Just switch the thermometer from one side to the other and give it a few minutes to acclimate. Taking both readings on the same trip within minutes of the other should minimize any variation due to changes in ambient temperature.

For best results, do this test early in the morning (or after dark) so the cabin isn't warm from the sun. And make sure LO was selected immediately after engine start so the heater core never warmed up in the first place. However, drive long enough so that if either side of the DCCV isn't closing fully, the heater core has enough time to warm up and cause elevated duct temperatures. A short test drive won't cut it.

Can't remember if I asked, but please let us know if the compressor clutch is engaged (pulley face spinning) when the AC output is not cold enough. If engaged, that means the compressor has received the command to run, and you're probably looking at a performance issue such as low refrigerant, slipping drive belt, clogged cabin air filter, etc. If the clutch is not engaged, you've got a control problem, a very different issue.

Please keep in mind you may have more than one fault in play. There may not be one magic fix that will miraculously cure everything that ails you. You may have to find and fix one fault and then retest, repeating the cycle as many times as it takes.

 

Earnest, I’ve experienced what sounds like an identical air conditioning symptom with my 2005 S-Type, V6. Two years is a long time to suffer with insufficient air conditioning cooling - I feel for you.. While I encourage you to continue troubleshooting following the excellent guides you referenced on this forum, I thought it might be beneficial for me to share my experience.
When ideling and driving on city streets, my S-Type air conditioning was not cooling the cabin. However, once on the freeway and over 65 mph the cabin quickly reached the desired cool temperature.
Some research and a helpful YouTube video seemed to provide a possible solution.
I learned that our S-Types are fitted with scroll type compressors. A YouTube member, “centurybob” has a useful post: You could also google scroll type auto air conditioning.
Centurybob points out what seems to be the same symptoms your S-Type is experiencing. If you listen to his entire post, he even mentions S-Type Jaguars as having this common issue. Have you had your mechanic check the HVAC pressures? When my mechanic tested my S-Type, he found the same pressure problems. I decided to have the control valve replaced. The new part was not easy to source, but it was under $50. The labor and refrigerant was a few hundred (same as replacing the compressor, but without the cost of the compressor). The compressor is located on the driver side for US models, left hand drive, on the lower portion of the engine compartment. Access is from below, after removing the belly pan.
Immediately my S-Type air conditioning was performing excellent. Unfortunately, after about 2 years and 18,000 miles, the same problem returned. Now however, the compressor was leaking refrigerant from the main housing. I could see the refrigerant after removing the belly pan and looking at the compressor. A new compressor was necessary and was installed. There are several excellent online sources that offer lifetime warranties. I’ve been good now for over a year and 14,000 miles.
In hindsight, I probably should have just replaced the compressor and not taken a chance that replacing the control valve would be a long time fix.
To my understanding, S-Types fitted with V8s have the same air conditioning compressor, but it is apparently somewhat more difficult to access.
I hope you find my experience helpful, and be sure to post what you determine your problem as and what you decide to do.

 

That's a very helpful video. One more thing he could have mentioned, though. Jaguar issued a bulletin for an optional procedure to override this control valve, and make the compressor run at full capacity all the time. This was intended for complaints of inadequate cooling at low speed. I've got some details in middle of post #4 of the troubleshooting guide, including a link to the bulletin.

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


The X-Type used the same compressor, too. You'll see a link to that section of the forum, showing how easy the modification is.

Other vehicle manufacturers used this same style of Visteon compressor, but as far as I know, Jaguar is the only one saying to override this valve if desired.