I have been having mild problems with the AC system this summer and they seem to be getting worse.

At the beginning of the summer the air coming out of the vents were 48-50 F. I took it local and had it vacuumed down (been 5 years since it had been done) and recharged to 27 ounces (it was only a couple of ounces down). The car still ran at the 48-50 degree area and while it was enough to cool the car, I knew that seemed out of bounds.

In the last 4 weeks the vent temp has risne to 58-60 degrees. I took it by another shop nearby and they found a loss of refrigerant to be 8 ounces. However I had them do a 30 minute vacuum test after which they refilled and zero indications of a leak. It still did not cool properly. Then after about 3 weeks I decide to do a top off ( very wrong, I know) It seemed to run a touch better, but still not optimum. So I took it to one of the shops nearby who had done the original refill. They purged the system and saw my top off had added 8 ounces on top of the 27 that was still there. They recharged to 27 and the 1.6 ounces of oil they got out and it is still cooling in a lousy fashion.. They spent about 45 minutes under the car looking for an signs of dye that they had been there from both recharges and found nothing!. They indicated the high and low pressures were in range

I can sit in garage and turn it on high with Low setting and just as the compressor is starting to really cool, it then goes off and comes back on shortly and repeats the same cycle.

I never use the auto climate control and usually set the system to "low" and recirculate and just adjust the fan speed. So that takes a number of things out of play as a cause. The DCCV is fine. The reading on the gauges do not indicate anything being out of range or any restriction. The condenser is clean. The cabin filter is new ( but since I set it low- the I do not deal with the fresh (really quite dirty in Dallas) air. The sensor above the ignition has been cleaned.

The compressor is 10 years old with about 70K on it, but in Texas heat. Jag replaced it in 2012 due to a faulty valve and the typical idle non-cooling.

So several questions:
1. Are these the symptoms of a failing compressor (zero leaks anywhere around it and zero bizarre noises)? I lean toward just getting it replaced, along with the The shop can put it in for about $190 and they are cheap enough on Rock.
2. Could this be something as simple as the pressure sensor being out of whack?
3. How would I lose 8 ounces and not have a leak. The suggestion was that some compressors have a relief/release valve and perhaps due to something it released some refrigerant. ( I don't think that is present on this compressor).?
4. What else would command the compressor off with a proper charge and the pressures in normal range?

Thanks
Tom in Dallas/Plano
2005 S-type 3.0, 127k

 

Hey tom. Your initial temp reading is high with things working correctly. You should see 38 to 42 at the vent. If it held the vacuum like you say then that could point to a faulty expansion valve or semi plugged drier. The loss of freon is a little more baffling. If it is losing it on the gas side you will not see evidence without a freon sniffer. Especially a slow one. I would get a cheap sniffer and check things out. Also make sure the cooling fan is humming along at at least 80 per cent when ac on and idling. If you find a leak and have to do a recharge see if you can access the back of the compressor and do the spring swap mod. You could also clamp off the dccv hoses while checking just to triple check that dude again while testing. A faulty pressure switch will surely cause cycling. Only way i know to remedy that is to replace them. Hook in to your sdd and see if you can get ac readings. I do not know if it does that. The low pressure cut out should be near the drier. High near compessor. It does not take much to send the system too low and set off the low one. Good luck buddy

 

Your compressor is probably fine. Same for the expansion valve. The short cycling of the compressor is your big clue, especially since the refrigerant quantity is known to be correct thanks to the full evac/refill.

If the compressor was bad, or the clutch was slipping, the clutch would be engaged continuously, trying to reach the desired results. Instead, it's being commanded off way too early, for reasons still undetermined. That tells us the compressor is likely working okay, but is not being allowed to do its job fully.

In my over-inflated opinion, the evaporator temperature sensor is the likely culprit. If reading low, it would be telling the controller the discharge air is at the desired target of approximately 38F, when it's really more like 50+F. The idea is to keep the evaporator as cold as possible, but without excess ice forming, so 38F is the ideal target. Please be aware there is no pressure sensor on the low side, unlike most systems. With the majority of vehicles, system pressure at the evaporator is used to indirectly determine discharge air temperature. The Jaguar system cuts out the middle man and directly reads the discharge air temperature for more precise control.

At the troubleshooting guide, please see posts #3 and #4 for more details of the evaporator temperature sensor. It is the same part number as the two duct discharge temperature sensors. Post #3 has instructions for measuring the resistance of the sensors. Let the car sit for several hours in the shade so all three sensors are the same temperature, and then compare the resistance values. I'm willing to bet your reputation you will find the evap temp sensor out of whack.

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


Another possibility is the AC pressure sensor, located on the high side. This is the only pressure sensor in the AC system. Details of this sensor can be found near the end of post #5, including other conditions which can trigger the controller to shut off the compressor clutch. I don't know of a way to accurately test this sensor, so gambling on a new sensor is probably the easiest method. It can be replaced without discharging the system.

One last possibility is poor airflow through the condenser, causing the high side pressure to rise too high. In that case, the AC pressure sensor will report this and the controller will shut off the compressor clutch as designed. Do the airflow test with the rag across the grill (post #4) to make sure airflow is adequate with the AC running.

Of these three possibilities, I think the evap temp sensor is the most likely culprit.

 

Thanks. I have no symptoms of a bad of a bad expansion valve. I used the Icarsoft for the JLR and it runs 43 data points on the CCM/HVAC and nothing seemed out of whack. It even showed the expansion vale opening and closing as one would expect at different temps between 35 to 39 degrees, unless it is the temp sensor for the evaporator. I have Freon sniffer and found zero. Two different shops in the last 4 weeks have done recharges for me and I was down on the first one, but they held a vacuum for 30 minutes and no issue. I then added some Freon as a top off to see if that helped and all that happened was to overfill the system when I did it 4 days ago. Yesterday a different shop did a vacuum and recharge and tested the vacuum for an hour and no issue. They also spent another hour going all over the AC system and no leaks. Schrader valves are fine.and no leaks. Cooling fan does exactly what it is supposed to. The AC pressure valve is on the drivers side near the top of the engine and near the radiator.and I tend to lean toward that and /or the compressor.

Would I not have moist type air coming in the cabin in the event of problems with Desiccant Bag?

I think replacing the AC pressure switch, the bag and perhaps the compressor is perhaps in order?

How would I clamp off the heater hoses without damaging them, although I do not feel anything like heat coming into the cabin on any of the vents. Something is commanding the compressor off, when it should not.

Thanks
Tom

 

You can buy special clamps, but I got small long nosed vise grips from Harbor Freight, wrapped the jaws with electrical tape and ziplocked them to stop them opening or falling off.

 

Sounds like you are hot on the trail. See my previous comment about the evap temp sensor likely being bad. If this sensor is sending an inaccurate signal, the computer will happily control the system to the wrong temperature, and be totally unaware anything is wrong.

If your scanner lets you read the computed value for this sensor, let the car sit overnight so the sensor is at ambient. Without starting the car, read the value and compare to ambient. I suspect the value will be substantially (edit) cooler than ambient.

If your scanner also shows the two duct discharge temp sensors, they should all be at roughly the same ambient temperature after sitting overnight.

I'm surprised neither shop suspected the evap temp sensor, or possibly the AC pressure switch. The Jaguar HVAC is a bit different than most vehicles, but's it a Visteon system also used on SAAB, Saturn, and a few other brands.

The desiccant bag is sealed within the refrigerant loop. It has no direct effect on the external airflow through the evaporator and into the cabin.


Depends on the condition of your money tree. I planted one several years ago, but my kids killed it off before it could bear any fruit.

In your situation, I'd certainly investigate the evap temp sensor ($20?) before digging deeper elsewhere.

 

Thanks, I think you are on the right path. When I put the Icarsoft for JLR on the car and ran through the live data feeds on the the CCM/HVAC, I saw where the compressor was getting commanded off by the min and max temp of the evaporator which was showing the range from 35- to 39 regresses (which I assume is about where it should be), and I know that it is not in any way the temp of the evaporator. Is there any reset of the system that might clear that?

How much does the pressure sensor in the front of the car have to do with temps? I am assuming that is only has to do with pressures and that does not appear t be my issue..

I am guessing the Ford part works as well and probably the same group made the one for Ford and Jag?

Thanks

Tom in Dallas/Plano
2005 S-Type 3.0 127k

 

Gotta back up for a minute. Are you positive the evaporator is really that cold? If the DCCV was not closing fully and dumping unwanted heat into the ducts (downstream of the evaporator), how would you know? In the troubleshooting guide, post #2 has two simple methods to confirm the DCCV is behaving. One method is as simple as pressing some buttons, and comparing duct temp to ambient on a test drive. Another option is to clamp off the heater return line. I know you previously said the "DCCV is fine", but I want to be absolutely sure the test was done correctly.

None that I know. If the sensor is bad, the fix is to replace it. If still hesitant, you can swap with one of the duct discharge sensors.

The AC pressure sensor primarily protects the high side from going too high, and will shut off the compressor if needed. But it's more of a last ditch thing and typically doesn't need to do so.

It's not impossible the AC pressure sensor is at fault, but far less likely than the evap temp sensor. Also, the evap temp sensor is super easy to check, so definitely look into that first. Have you compared the sensor's value to ambient, as previously detailed? That simple test should quickly confirm or rule out the evap temp sensor as the root cause. Can't get much easier or more definitive than that.

I replaced one of the three sensors several years ago. IIRC, the existing part had a Ford logo on it, as many of our parts do. I know the part I installed was Motorcraft (Ford). It has worked fine all this time.

 

The DCCV checks out fine. However I do question one of your test on the DCCV. It is susceptible to picking up ambient temps from the engine, so as the metal of the engine and surrounding metal that the pipes are attached, as well as a nearby heat shield it has to reflect some of those values. They were still lower than the temps near the radiator, but were essentially the same as the metal it is attached to. I understand the DCCV can dump heat into the cabin and area, as I had one blow when still under extended warranty and out went the CCM, so I have changed that routinely whenever I had a coolant flush done. However if the DCCV was dumping heat into the area, that would not command the compressor to turn on and off quickly as they relate exactly to the temps at the evaporator that do not appear accurate.

I will look again at the ambient to the sensor's value (how do you do that? as my scanner or the SDD will show that), however in the scan it showed the ambient temp.to be accurate. Perhaps you are suggesting looking at something different than I did and if so, please tell me as you are the one with the knowledge. I have enough knowledge to be dangerous to myself- ha ha!

The main things that was out of whack was the temps showed at the evaporator just sitting in the driveway and there is no way with a fresh start and running the car at idle for about 3 minutes that my evaporator is at 35-39 degrees (the points at which the compressor turns on and off). I know for a reasonable logic that the evaporator is not that cold. The only other difference was the driver's side heat sensor was showing at 41 degrees and the passenger side at 50 degrees. However I am not sure what those values should be. As I had said before , I never ever have use the Auto setting on the CCM for AC and always keep it at low and on re-circulation and merely adjust the fan speed.

I have a 2005 not 2002, so do the sensors all seem to be the same ones?

Thanks

Tom

 

Not trying to bust your chops, but exactly how did you prove this? Did you measure and compare the line temperatures with an infrared gun? Did you check the duct temps on a test drive, using a clip-in thermometer? Did you clamp off the return line and then measure duct temps?

If you measured duct temps, did you rely on scanner data or use a clip-in thermometer? I'd much prefer the latter. Even if a cheap pocket thermometer was inaccurate, it should show the same value (potentially erroneous) on both sides if temps really are the same. Not so with scanner data, as the sensors could be bad and then you'd have to determine if you have got an actual temperature split or an indication problem.

I'm starting to think you may have a minor second issue. More in a minute.

Blasphemy!

Yep. If you have any doubt about your results, do the check of the duct temps on a test drive. Not quite as accurate, but far less susceptible to other influences. Important set-up details in the troubleshooting guide. Switch the AC button to off so the compressor doesn't run and cool the air. Select manual LO. This applies full power to close both DCCV valves, so no heat is applied as air passes through the heater core. Go for a test drive so the system intake (base of the windshield) is not drawing warm air from the engine. With no heating or cooling of the air in the ducts, the temperatures on both sides should be very close to ambient. I've tried this several times over the years and the duct temps were always within 3F of ambient.

My thoughts were to turn the key to Run to power up the scanner, but don't start the engine yet. We don't want any heating or cooling for now. We just want to record what the sensor thinks is pure unadulterated ambient input. Do this first thing in the morning after everything has cooled overnight.

Under what conditions? First thing in the morning, without starting the engine? If so, the evaporator temp sensor is okay, and the problem lies elsewhere. Sorry for all the questions, but I want to be sure we're not inducing errors with our test methods, or inadvertently making false assumptions.

Maybe it is accurate? If ambient isn't too hot and the car was parked in the shade, perhaps it could cool that quickly. I don't really know, but it doesn't seem too far-fetched.

Its also possible a sensor is only accurate over part of its range. Recently the temp gauge on my pickup was reading cooler than normal. On a cold start, the initial response was normal, but the needle never reached its regular spot. I got a new sender and compared both before installation. Heated in a pot of water, both showed the same resistance for most temperatures. But as the water got above 170F, the old one stopped climbing. The resistance stayed put as the water got warmer. Obviously a bad sensor. The replacement fixed the problem.


In manual LO, with no heat added to either side, the two duct temperature values should be very close to each other and to the evaporator temperature. Something isn't right on the passenger side. This is the second problem I mentioned earlier. Is this a bad sensor? Or an actual temperature split? If indication only, this may be a moot point if always running in manual LO, as the two duct temp sensors are out of the picture. But if accurate values (confirm with a pocket thermometer), the passenger side of the DCCV is letting heat into the cabin.


Can't remember where I got that Motorcraft number, but I believe it's applicable to all years. You're more than welcome to get the official Jaguar part, but I bet it has a Ford number or logo on it.

One word of caution: 'Analysis Paralysis ' seems to be setting in. We may never be able to conclusively prove or disprove any theory ahead of time. Sometimes you just gotta start with a reasonable* guess and see what happens.

*Preferably cheap and easy.

 

Just had another quick thought while in the shower. (Sorry for the mental image)

Trying switching off recirc mode for a test drive. Just a wild hair, but what if the controller automatically switches to some special protective mode with LO and recirc manually selected together? I've never heard of such a thing, but was trying to think what you're doing differently from others. Simple enough to rule out...

 

I appreciate your help and do not at any point ever mean to sound rude or unappreciative.
My problem is that the compressor is short cycling- it run exactly in sequence with the temps (by the scanner) of the evap. being at either 35 degrees or 39 degrees. This happen as soon as I start the car in the morning and before any coolant on the car has done any major uptick in temp. I will ask- even if the dccv ( and as I said I know all about it's faults) was dumping some small amount of hot air into the cabin- how would that command the compressor to short cycle. I might, as you indicated, have 2 problems, but with my limited knowledge, I don't see the DCCV commanding the compressor off and on. We are talking about the compressor running for about 15 seconds, going off for about 20 seconds and then back on for 15 seconds or so. This happens out of the gate in the morning. Under those condition with 85-90 degrees of temp is there any way that the exvap is actually at 35 degrees.

The temp of the ac coming out of the vents is within a degree or 2 all across the board. The compressor just does not run long enough to be effect I will try later the non-ac and the ambient temp and see what gives..

Yes I used an IR temp gauge and the clip on the vents. My point on your test about the temp of the heater lines is that they are metal and if the surrounding metal heats up to a certain temp- then how would the heater pipes not inherit the same temps?

I looked at the sensors online and they look the exact same except that Jag adds a 100-110 bucks to the price. How long did it take you to get the evap temp sensor out? I am not worrying about trying to measure as a new sensor either would solve the problem of not and at 25-34 bucks a minor investment.

I just checked with the AC off and KOEO and the ambient temp on the dash is 76 and the inside temp according to the scanner in 75 and the temp at the heat sensors is 71. The scanner says that the ambient temp is 75- so that seems close enough. The cutoff temp that showed from the evap was 68, but since the AC was not running, I don't think that temp is relevant.

I will try and run the clip later in the day without ac and in a low position and see if they are close to ambient. I had recently changed the ambient temp sensor to a new NTK, but nothing changed on what it showed the temps to be.

Since the 2 sensors are out of the picture with the AC on low- perhaps the temps being reported have little meaning??

I go back to what seems to be a relevant question- even if the DCCV was dumping in heat, how would that cause a short cycling of the compressor?

Thanks

Tom

 

Thanks Scott. My compressor is a newer version and muck like the one that Rick (Joycesjag) installed and I have no valve on the back to alter. If i did, I would have had that switched without a second thought. I have a Freon sniffer, but nothing so far. Fan is humming along right where it should be. I see the pressure switch and unfortunately there is no way to command it open all the time to see if it is the culprit. I think I am getting a misreport on the exact evap temps and that runs right along with the compressor going on and off. I also do not think I have a leak. Twice in the last 4 weeks I have had the system recharged and they both help long vacuums and the second one showed, after I had tried a top off, that I had just added more freon in than was necessary. on top of what was already there. I am hard pressed to think that even if I had trouble with the DCCV that it would command the compressor into short cycling.

Thanks

Tom

 

I think that evap sensor reading is very relevant. Even with the AC off, it’s still measuring air temperature. And it thinks the evaporator is about 7 degrees cooler than it really is. The controller will happily adjust the system output to this erroneous input.

If 38F was the correct target temperature at the evaporator, you’re going to get 45F instead now. The error may be worse at cooler temperatures, too. You’ve got a 7F error around 75F. It may be 10F or more at 38F.

You mentioned your compressor is the later modified version, with no pressure sensing valve. That valve made the compressor self-regulating to some extent, reducing cycling. Without this valve, the compressor runs at max capacity, either all or nothing. That alone will cause frequent cycling, but I bet you never noticed it as long as the air was cold. It wasn’t until you started investigating the warm air that the rapid cycling became apparent. It may have been doing this all along to some degree, and the bad evap temp sensor made it worse.

Access stinks to replace the evap temp sensor. It is above the gas pedal on LH drive models. Drive the seat all the way back and raise the steering wheel. You’ll still have to stand on your head to get under there. You can only get one hand in there, so undo the connector first. Practice swearing ahead of time.

Back to the DCCV, it should not affect the compressor cycle rate, exactly as you were thinking. I only mentioned it because you were showing one side significantly warmer than the other. If indication only, as seen by the scanner, it won’t affect operation in manual LO. But if your pocket thermometer also shows a split, something isn’t right with the DCCV. This would be in addition to the bad evap temp sensor.

 

Yesterday i did mu early morning drive with ac off and just fan at low. Did it both with recir and fresh air. After the car warmed up the ambient temp was 83 degrees (both shown and measured by the temp control ) according to the scanner. The temp from the vents showed at 88 degrees, so if I had a DCCV allowing some heat in the area, it would appear minimal or was reflected the temp from the engine and as we both know that would not command the compressor on and off. I watched more intently on the heat temp sensors for both sides and they were making adjustment from the drivers side from 40 degrees down to 39 and the passenger at 42 down to 40.

At this point, I think the evap sensor replacement is in order and I might as well, for the fairly cheap price change the pressure senor up front. I assume those 2 could impact turning the sensor on and off. I am fairly certain that if the compressor was allowed to run longer, I would have a zero AC problem.

THOUGHTS?

and thanks again for all the help, but you are the expert.

Tom

 

I would suggest only changing one part at a time. In this case, the most likely culprit is the evap temp sensor.

A good rule of thumb, reflected in my personal motto below, is to avoid making too many changes at once while troubleshooting. Let's say you can't stand it, and just want to change both parts. You wrap up the job and go for a test drive, only now the problem is worse! Was the new evap sensor bad from stock? Or was it the AC pressure sensor? Or maybe the parts themselves were fine, but maybe a connector didn't get fully seated or something else got knocked loose. Where do you start troubleshooting? If you only worked in one specific area, you'd know where to begin. I do not care to discuss how I learned this...



Sure, write one comprehensive troubleshooting guide and suddenly you're the expert...

 

Did a little more digging to find how I came up with that Motorcraft part number. See post #8 in my thread from 2013, when I was still wet behind the ears in the S-Type HVAC world:

https://www.jaguarforums.com/forum/s...94/#post802726


All 3 existing sensors in my '02 had a Ford number cast in the body:

XW4Z-19C734-BA

Search online with that number, and you'll find multiple cross-references to Motorcraft YH1504. The way I understand it, the long number is what Ford used in their factory supply chain and dealer parts departments. Motorcraft is their pseudo-aftermarket spin-off for genuine Ford parts.

I also looked at official Jaguar parts here:

https://www.jaguarparts.com/

The same Jaguar #XR853162 was used for all years on the S-Type. Extrapolating all that, you should be fine with a Motorcraft YH1504.

 

Any update?

 

I have gotten the Ford version of the evap temp sensor and have not gotten emotionally up to act as a contortionist yet. Further the temps have been down- so it is not the best time to test. I spoke to a well known European shop about the issue and the guy that would deal with my car, if I decided to bring it to them. has owned S-types and indicated he has replaced many of the evap tenp sensors on Ford cars, but as we talked through the issue- he felt I (we) had narrowed it down.


Tom

 

hey tom

do like i do and have a young bendable skinny kid do it for a couple jacksons