The air conditioning has never worked perfectly in my 2012 XKR since I bought it in 2019... The compressor clutch wasnt very strong. A common failure.

It would blow cold, but only consistently while driving at highway speeds, and only after I had been driving for awhile. Stop lights and city driving weren't horrible, but they weren't the most comfortable. It worked well enough to not need a repair until it failed completely.

When the compressor finally died last December, I had the compressor replaced, dryer, etc... The basics. The shop did a pressure test, it passed, and they sent me on my way. Since it was getting cooler (I'm in Texas), I never really needed it to work hard.

Now it's warming up again, and it's finally time for the system to work hard. However, I've noticed strange behavior. The vent temps will be slightly warm for 10-20 seconds with a musty odor... And it'll quickly blow cold again for a few minutes. This cycle repeats for 20-30 minutes of driving and eventually subsides and the temps will be cold more consistently. The brief warm cycle still occurs, but less severely.

The strange thing is that I can park and idle, and this vent temp cycling won't happen. The car idled in a parking lot yesterday got 30 minutes, and the temperatures were cold and comfortable. As soon as I started driving, the temp cycling started again... Slowly subsiding until I got home.

My gut tells me there's a leak and the refrigerant is low, but I've inspected the system for dye leaks, and haven't noticed anything

Does anyone have experience with this? Is it just normal operation to maintain the set temperature? I have no frame of reference.

Anyone have a diagram handy of the spots I should focus on for leak checks? Are they all visible with the engine covers in place? Maybe I'm missing a connection to check.

Does this behavior seem abnormal, and I should start looking at sensors to replace?

 

Need to post hi and low pressures. That's the only way to troubleshoot AC. Also get a duct temperature gauge for about $10.
What brand of compressor was installed? Many cheap chinese ones out there.
Do you know about the DPS problem?
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Can I read pressures through SDD? I don't have a gauge setup, but I do have a full SDD.

The duct sensor I have is too slow to respond to the vent temperature fluctuations. I've been looking for a way to record vent temps to a logging device via thermocouple or similar.

I'm guessing this is the DPS issue you mention, but how likely is it to occur on a brand new compressor? I'm waiting to hear back on brand of compressor installed.

https://static.nhtsa.gov/odi/tsbs/20...94594-1020.pdf

 

No you need gauges.
It's just what you run into if you can't DIY the repairs. Hopefully the shop you used will stand behind their work.

The refrigerant has UV dye in it from the factory. If you suspect leaks get a black light(UV) flash light as they are cheap too.
Read up on the DPS valve as it's common and has definite symptoms. I am suspicious that you got a cheap chinese compressor installed.
Now sometimes those work just fine but again sometimes they don't.

Did you get a warranty on the compressor?
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The radiator fan might very well be the culprit. Had the same symptoms with my 5.0NA XK. Easy to diagnose, soldered contacts inside the electric motor assembly fail due to constant vibration. So the fan doesn’t turn on intermittently, resulting in no air flow through the AC radiator when the car is stationary ie on a stop light. Then the air flow is restored when the car starts moving or the the electric current gets restored spontaneosly, resulting in the normal AC operations.

 

I once fixed a poor performance on my Volvo, by washing the clutch assembly with brake cleaner. The clutch plates had been slipping.

 

Yeah a/c problems can send you down a lot of rabbit holes as i found out. The actual pressures as club said are the best start. Check with a/c off and both should be about the same. Check again at lo setting and report those at idle. Then slowly bring up rpm to about 2500 and record what happens. It is way easier to have a helper either running the throttle or video the gauges. All pressures are relavant to ambient temp and refrigerant charge

 

Using a sniffer in a closed area is the most reliable. I've seen leaks that didn't offer any UV sign, and it wouldn't have helped anyway as the leak was on the backside of a line where abrasion had created a very tiny hole. A sniffer located that leak after many hours of searching.

 

Here is a page from the service manual with the normal pressure ranges of the AC system.





See if you can get any pressures and post back. The sniffer is a valuable tool as well and now they are not too expensive but there is a wide price range. I know my HF sniffer throws an awful lot of false positives.
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https://www.jaginfo.org/threads/air-...-valve.114235/
It's a $70 part, but requires refrigerant extraction, and removing the compressor to get to the part.

I have the same symptoms, but have not dealt with it yet.

 

Yes I have a large thread on the DPS with many details including the right parts numbers and the fact the Jaguar TSB has some errors in it.
Take a look as it's a BIG project.
Also see my final recommendation that it's much better to just plan on a compressor replacement with a warranty.
AC DPS Valve Problems
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I agree with Andrey. An intermittent condenser (radiator) fan could cause the symptoms that you describe. Since you are not into refrigerant gauges but do have a command of SDD, start with what you know.
First, check the fan bearings: Give the fan a spin manually. It should turn easily and even coast a bit. Access is difficult and the fan can start anytime that the battery is connected. Even with the ignition off.
So, a "tool" that works for you is appropriate.
If the fan turns freely, use SDD to control the fan. Connect your battery maintainer and run the fan at different speeds and for an extended time to check for failure.
If the fan passes your tests, visit the AC shop again.

Keep us posted on your solution.

Bill

PS: Don't worry about "the clutch". There isn't one. The compressor is "engaged" by a solenoid.

 

My Mazda did something quite similar. The fault was the system was overfilled with freon.
wj