I have recently been experiencing strange behavior from the cooling system. When I start the car in the garage the A/C comes on and cool are is felt immediately but after driving a short distance, maybe a quarter of a mile, the air gets warm and stays warm for about a minute then turns cold and works perfectly after that. If I make a stop for a short time, the A/C works perfectly and no warming up for a short time anymore. I usually operate on manual mode. A month or two back I had the reverse happen when it was cool outside, in the low 60's and the manual temp was set around 74. When I first started the car there was heat but then it went away and replaced by cooler air within a short distance and the only way to get heat back was to increase the temp to around 78 or 80.
Could this be a sign of something ready to get worse and stop working all together?

 

Sounds like DVCC to me.

 

Sure does sound like it.
Probably the valve seals are starting to swell and bind, it's a well documented failure on the DCCV's. Just done mine.

 

Interesting problem. Let's start by defining "warm" and "cold". It would be a huge help to have numeric values from a thermometer in the dash, for comparison to exterior air. If you've got air WARMER than ambient, you've got unwanted heat being dumped into the cabin. If the "warm" air is below ambient, you've got at least some cooling in effect, although unwanted heat is still a possibility.

Also, are you only adjusting the fan speed in manual mode? For troubleshooting, that doesn't help much at all. Bump the temp setting up to HI or down to LO. This bypasses some of the sensors and is a great aid for troubleshooting.

Please try this, specifically the troubleshooting steps in posts 2 and 3:

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

I'm curious to see how the dash air responds in HI or LO. Also, pay close attention to the air temp on both sides of the cabin. I'm leaning towards a bad temp sensor for the evaporator or the discharge ducts. The guide linked above has some tips to diagnose them, in post #3. If both sides misbehave, the evaporator temp sensor is more likely. If only one side acts up, you're probably looking at that discharge duct temp sensor. Keep in mind the two discharge duct temp sensors are out of the equation in HI or LO, so use those settings to your advantage when troubleshooting.

The DCCV is still a possibility, but much depends on checking the temperature from the ducts on both sides of the cabin. Since you're getting uncommanded warm air for only a brief moment, and then all is normal, it's not very likely both sides of the DCCV have the same intermittent fault. It's more likely to have a faulty common input. All bets are off if only one side acts up.

 

Replaced our DCCV a couple months back. Took 20 minutes.

 

There was a time when I would do just about any replacement of a part attached to the engine or body but I am afraid that those days are behind me now. I can only hope that my local garage will be reasonable and maybe even use a DCCV that I can get cheaper than the Jaguar dealer's price that they prefer to use. ( I understand why, but....) 20 minutes? That really hurts.

 

Where did you buy the DCCV? Thanks.

 

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