Morning everyone,

I'm suffering a weird climate control / air conditioning problem.

• Back in May (you know, when it was really hot) the a/c in the car appeared to be running out. We'd only had it regassed last year, so I was assuming a leak somewhere.
• Some time passed and I had it regassed a few weeks ago, with a company that uses a UV dye with the gas so they could find a leak if / when it occurred. The air conditioning worked fine as I drove away.
• The next day, the air con seemed to have failed again, the cabin fans were blowing warm air only. However, if you selected "windscreen mode", the air coming from the windscreen vents definitely felt air conditioned.
• Turn "Auto" back on, and the warm / un-air-conditioned air was back.

This led me to thinking that the issue is with the humidity/temperature sensor in the cabin. My thought process was that the air conditioning was actually functioning fine, but the climate control didn't think that the cabin was warm/humid enough to need the air con running.

I tried last night to find the humidity/temperature sensor under the drivers side (RHD) dash using this diagram but failed. My plan was to disconnect it and see if the climate control worked any differently.

One further thing: When I set the climate control target temperature very high or very low, the blower speed does increase. When it is in-the-middle (~19-20 degrees), the blower speed slows. This may suggest that the car at least knows the temperature inside the cabin, but it might just be a factory setting.

Questions:

Has anyone had a similar issue, and what was the resolution?
Can anyone guide me to the sensor under the dash?
Have I missed anything obvious in my troubleshooting?

Many thanks in advance.

 

The easiest way to verify if the system is full is to check pressures with an AC gauge set. Considering you just had the system checked and regassed unless you had a major leak you are right in looking at the rest of the system.

 

Update:

I've managed to locate and remove the temperature / humidity sensor.
With the sensor removed, I activated the climate control and it's essentially performing exactly as before - suggesting that the sensor possibly wasn't sending any data to the climate control.

Looking at the sensor assembly, it appears to be a standard Ford sensor unit in a Jag fitting. I found one at britishparts.co,uk - part number C2P2941. I've ordered one and will update this thread once tried.

 

I have almost this exact issue. Recharged my car at a local shop the other because the dealer said they always start with a $450 "A/C tuneup" before checking anything else. Even after the recharge (.5 lb added) though, my car still has a hard time dealing with humidity. So I'm thinking of taking my car in to the dealer to try and take advantage of the last few months of my warranty and hopefully have them figure out what needs to be done over just adding refrigerant. I remember there was a Jag TSB some time back about poor climate control performance and a need to replace a valve or sensor of some sort. How hard is it to get to the sensor and how much was it to replace?

 

Is it the sensor behind the little vent in the trim panel behind the steering wheel?

 

There is a variable displacement valve on the rear of the compressor that is susceptible to sticking after time. Typically the dealer will replace the entire unit though its really just the replaceable valve that's stuck. The valve position is regulated by the AC system demand. Just for your consideration.

 

There is a TSB about the pressure switch on the back of the compressor. It needs to be pulled out and the spring position switched. It's a royal pain to remove the compressor,
if you have small hands, it is possible to change the switch in the car.

 

Interesting - is that this TSB https://www.jaguarforums.com/forum/a...aircon-tsb.pdf ?

 

That's the TSB I've seen. Does anyone know if there a defect in the original DPS valve design that's been addressed/redesigned (like the water pump) or is the TSB simply there to point out the DPS valve as a likely culprit for AC issues?

 

That's a later TSB I think, now calling for replacing the valve.

 

AC broken, and it needed a tow??? Did the front of the compressor come off or something? I can't make this correlation.