I'm hoping someone here who has more knowledge of air conditioning systems than me can help me out or point me in the right direction.

A couple of weeks ago on a long road trip my AC started acting wonky. I was driving on the highway cruising 75ish, it was 95+ Farenheight with high humidity and my AC would randomly stop working. The cabin fan would keep blowing and air would blow through the vents just fine, but it would only put out ambient air. It would blow cold for sometimes an hour and sometimes only 10 minutes. Turning the climate control off and then turning it back on a minute later seemed to cure the problem until it would quit again and I'd just reset the climate again. I had the AC on the lowest setting, cabin fan blowing at a lowish speed and recirculation on. I haven't had this problem at all since a few weeks ago and I've driven hour plus trips since then with the AC working just fine, but not in such extreme temperature and humidity. I did change the cabin filter just in case, but the old one did not appear to be all the dirty honestly.

Does anyone know what might cause this? Low charge, bad expansion valve? What seem to be the most common failures in the AC system on these cars?

Thanks for any help.

 

When you write that you had the AC on the lowest setting. would that be the temperature setting? So that would have been, given the outside temp and driving, a pretty good load on the system. This system is a "conditioning" system, which means it monitors temperature, moisture, etc and reacts accordingly. Were you uncomfortable in the car? Did it seem too warm for the setting you had selected? I had the system pressure checked at the dealer before "AC" season this year, since I acquired the car in the fall of 2020, and wanted to check it before I needed it. No issues. Working as it was supposed to.

 

The system is capable of handling the 95 temperature and the fact that the system resets means it's not freezing up or a refrigerant issue. It could be a compressor problem, but it sounds more like an control module/sensor issue.

 

My a/c has never failed me in Vegas! Even during our record 114 a few weeks ago.

 

I've narrowed it down a bit with some testing. The compressor and relay don't seem to be an issue, it's worked flawlessly the past month plus. It always engages when commanded by the AC switch inside.

It may be a sensor issue, I know this car has quite a few of them that interact with the climate system.

My next step is making sure the charge is correct and the expansion valve is okay. I've had an issue with other vehicles where a low or high charge resulted in some of what I am experiencing now. If both of those check out I'll probably need to dive down the rabbit hole of checking out the sensors.

 

I posted this a few years ago as there is a similar thread, but I have found the A/C system to do strange things if you attempt to control it yourself. Just using the temperature control solely works the best but direct control seems to cause the A/C (and heating) to do odd things.

 

Any chance you could link to that thread? I'd like to take a read through it.

 

There are multiple (here are a handful):

https://www.jaguarforums.com/forum/f...0/#post1512504

https://www.jaguarforums.com/forum/f...here-c-177195/

https://www.jaguarforums.com/forum/f...e-temp-188948/

However, you'll find the usual suspects in each thread.

 

The most common fault based on your symptoms is low refrigerant. This happens for many reasons including a leak or even multiple service checks when a technician hooks up a set of gauges and some of your refrigerant is released into the hoses of his gauge set. If done multiple times and your refrigerant was at the low threshold to begin with, it could tip the scale. Most often though it is caused by leaking schrader valves. It's important to ensure the red and blue dust caps are in place to keep dirt out of the schrader valves. Low refrigerant will cause the compressor to cycle on and off giving the symptoms you described. As the ambient temperature and humidity changes, the symptoms may disappear because the refrigerant gas has different pressures in the system based on ambient temperature. Best way to diagnose an AC system is to hook up a set of gauges and ensure you're within the correct high and low pressure readings based on ambient temperature.