I have a strange problem with my 2006 3.0 S-type with sat nav.

When I start the car the air conditioning works fine. However, after a while it just blows hot air. This happens for example after a short stop, when I start the car again, or after a +/- 60 min drive on the motorway. There is no difference between automatic and manual mode, passenger or driver side, or the selected temperature or mode.

If I park the car for a few hours, the problem disappears, as if only a cold start is enough for the AC to work normally.

What I have done so far:
- Top up the AC refrigerant at an AC shop. No faults were found, although the system was at about 1/3 of the required amount before I had it topped up.
- I had previously replaced the heater valve because of another problem: the difference in heating between the passenger side and the driver's side.
- Checked the clutch relay. I replaced them with different relays, but to no avail.
- Checked if I could hear the clutch engage. When the problem occurs, the clutch makes the clicking sound when you press the AC button on or off.
- Checked for DTC faults, none found.
- Read all the previous threads on the forum

My first thoughts:
- I know the AC module is prone to failure. But I would think that this is not the problem, as it works initially, just not after a while, a new start with a warm engine.
-Could it be the heater valve that is causing the problem? It could be a bad one that just fails when it gets too hot or something, but that seems a bit far-fetched.

Anyone with a clever idea?

 

Did somebody say AC blowing hot air?!!!

First big question: How hot is this hot air? Often when the AC isn't cooling, people say the air is hot but that can be misleading. Is the air truly hot, indicating that heat is being added to the mix? Or is merely equal to ambient, meaning no cooling but also no heat? Big difference in how to troubleshoot, so please elaborate.

Second question: Have you worked through the troubleshooting guide? Most (but not all) scenarios are covered:

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

 

Yes the DCCV is a well known failure point and if it has not failed yet I would be very surprised.

Next problem is the longer you let this go the more likely you have also taken out the RCCM/CCM as well. Now these can be repaired and even upgraded with circuit protection to prevent this in the future. The idea was Jaguar improperly designed the circuit board so when the solenoids in the DCCV go bad and start drawing excessive current there is nothing to limit how many amps the RCCM/CCM board sees. So it burns a trace out on the board. Again well documented and somewhat common.

Take a look here as this web site has a massive amount of information on your problem.
RCCM Repair

Since your not in the US I can't say if you want to deal with international shipping or not but do some reading as they give explanations about what the problems and solutions are.
Have you removed the module and looked inside? It usually easy to see the burned stuff?
Here is a picture from the JaguarClimateControl website showing the damage.




Post back with some pictures if possible.

Oops! Looks like Karl beat me too it again!
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Thank you, Karl and clubairth,

Yest the air is indeed hot. It is really hot. Really really hot

Yes, I followed the guide you mentioned. It helped me a lot with my previous style. In this case it was just the fuse that I had to replace. However, the guide does not cover the situation where the hot air starts after a while. That's why I asked the question.

I can have a look at the circuit board. That is the next step, just wondering if it could be something else as it does not seem logical that a board would be burned as it works fine until it stops and it seems to be something overheating.

 

Hmm, this is a little different than the typical failure mode. A few quick thoughts, in no particular order:

You mentioned previously replacing the DCCV. What brand did you install? IIRC, Bosch was OEM. There are lots of poor quality aftermarket brands out there, with dismal reliability. Perhaps the internal seals are swelling up when warm and not letting the valves close fully when commanded.

Have you checked power and ground at the DCCV when the fault is active? I'm wondering if the problem is on the command side (electrical) or within the valve itself (mechanical).

Connect a scanner and watch the coolant temperature. Be aware the dash gauge is deliberately misleading, and will remain centered from approximately 180F to 230F. With a scanner reading live data, you can read the actual coolant temperature. Kind of a long shot, but perhaps the coolant temperature is fluctuating within that range. At 180F, there may not be a lot of heat to dump into the cabin, even if the DCCV was sticking open. The AC system may be able to overcome that to some extent, so the problem is not noticeable. But at 230F, that's a lot more heat available, in excess of what the AC can cool off.

On my '02 V6, I've noticed the heater output is marginal with the engine at idle speed. On a cold day, when coasting to a stop, sometimes the heat output drops off considerably. But at freeway speeds, the heater output is nice and toasty. The engine temperature, as observed with a scanner, remains fairly consistent. I think it's just the coolant flow dropping off at lower RPM, and thus less heat. So perhaps part of the issue could be all seems good driving slowly around town, with low engine RPM. But at freeway speeds, coolant flow through the heater increases and suddenly there is more heat than the AC can cancel out.

For more quick and dirty troubleshooting, see post #26 in the troubleshooting guide. It was suggested to clamp off the heater return line to block all coolant flow through the heater core. If the AC output is now normal, you know the DCCV was somehow letting hot coolant into the heater core.

Even though you've previously replaced the DCCV, be sure to run the tests on the replacement. These are detailed in post #2 in the guide.

Don't forget you'll want a little pocket thermometer in the dash vent to get a true idea what is happening.

 

Thank you all for your response. so i took out the climate control module, but so now obvious defects. Finally bit the bullet and ordered a new dccv. Made by Gates. No problems since!