When it rains, it pours! So, as you may know I just finished replacing my DCCV and aux pump due to lack of heat. Well, that fixed that, now something new! I tried searching on here but couldn't find anythig like I have! So, what seems to be happening now is the car not properly providing cold air. Here is the problem and what I can diagnose:

Start car, temp set to whatever it was when it was turned off (usually around 21C).
Nice hot day and car, so expect to cool down. I expect somewhat of a delay before cold air comes out of the vents. However, if you don't press anything and just wait, it never gets cold, cool and muggy comes out, but not cold. However, if you set it to LOW (still no change even after waiting a while) which turns off AUTO control, then press AUTO again and let the car do what it does, give it a bit (maybe 30 sec or so) and like magic, cold air like it should be! From then on it all works good. I can set it up to 30, burn my face off, then back down to 17 and freeze myself. And all vents blow the same temp (thought about the DCCV or RCCM going again).

So, from this I can conclude that the car can provide cold air, so the AC system shouldn't have to be recharged or whatever and the compressor, sensors and whatever else is involved in the system does function properly. My theory is that something isn't being told to turn on or open properly when the car is first turned on. By cycling through HVAC settings back and forth, whatever isn't turned on or switch on or whatever is told to start working! Therefore, I feel that everything is working properly, but there is some kind of misscommunication when the car is first turned on. Could the compressor just not be getting a signal to turn on? Maybe the ac clutch (or something) isn't properly (or being told to) engage? Or is there something completely simple that I'm missing! The one thing I haven't checked is if it is the switch from recirculate (which comes on automatically when you set it to LOW) and then I believe turns off when you set it to AUTO control again (or something to that effect). Anyone have ideas? Things to try, check? Is it possible that air trapped in the system could do this? (since I've had the cooling system drained and filled like three times in the last little while with all the work I was doing) Also, my wife told me that when she was having this problem today she left the car on AUTO settings, but when I just had a look and took it for a drive, the AUTO wasn't lit up, but in climate settings, it said everything was under AUTO control. Coeincidence or indication of whats wrong! I'd have to check this agian as I don't know for sure if she remembered right or if this happens all the time.

Why does it always seem that heat fails in the winter and cold fails (or does this!) in the summer!
Thanks in advance!

 

So, after a little digging around online, it seems like the first thing to check are fuses and relays, possibly an AC pressure switch (or something like that) and finally see if I can actually see the compressor clutch engaging (if the ac compressor is visable in that engine bay!). I'll be abel to give those a check tonight (short of the compressor clutch). Again, everything is working as it should, heat fine, all vents same temps, when working the AC is ice cold, and the blower is working as it should as when you set it to cold and its nice and warm out, the blower is full power trying to pump out that cold air to cool it down. Just no cold air until I mess around with the controls a bit!

Any ideas out there?

 

Could it be a flaky temperature sensor? And keep in mind that failing compressors are still able to provide some degree of cooling under certain circumstances before they finally give up the ghost. Over the past couple of years, we've seen a number of factory compressors fail here on the S-Type forum (including ours in May/June 2010)....

 

Thought about the temp sensor, but if you set it to LO, that should bypass all sensors right? Therefore it should just blow cold. I guess the compressor could be on its way out, but once I get things working, it continues to work and provide ice cold air. Maybe it is just having trouble getting going and once I play around with the controls, maybe sending additional signals to it to do stuff, it starts working. Just one of the many things that could be wrong I guess!

 

Don't count out a bad DCCV. I know you just replaced it but your symptoms point to it again? There have been a few reported to be bad after replacement. So it is a possibility.

When you ramp the temperature up and down you are exercising the DCCV between fully open and fully closed. After you have wiped the tracks clean (so to speak) the DCCV now response to small temperature change commands from your climate control unit. Until the car is shut off and the DCCV takes a set again and gets stuck at the spot it was in when the car was shut off.

How did the coolant look and was it flushed and changed when the DCCV was replaced?

You might try to cleaning the inside air temperature sensor. It's behind the small grill above the ignition key. It does build up crud because it's the only temperature sensor that draws air in from the cabin. So any smoke or dirt in the air flows across that one sensor. Any build up will slow or skew that sensors response. Do you smoke or does anyone smoke in the car?

All the other temperature sensors measure outgoing air into the interior. This air is almost always filtered by the cabin filter. The only time it's not is when you have the system in recirculate mode.

"Why does it always seem that heat fails in the winter and cold fails (or does this!) in the summer!"

Well it really does not but think about it for a minute. We don't use the heat in the summer so even it was not working how would you know? Well you will find out when you want heat which is in the winter!
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Ya, I know why the heat fails in the winter and cool in the summer! lol Just annoying!
The coolant is good, just changed it all out last summer and it still looks really good. I have cleaned the temp sensor inside, and nobody smokes, especially in the car! I hate to admit it, but the more I've been thinking about it the more it points to a sticky DCCV. Everything was working perfect until I tore into the system and replaced everything. And once I get it working again it works perfect for the rest of the trip, however long it is. And just like you said, by cycling through LO and up and down its telling the DCCV to open all the way then close, open, close a bit, and so on, therefore possibly unsticking the DCCV. I really don't want to tear into that job again! I think I will first try cycling LO to HI a bunch when I have a chance. Maybe there is just some stuff stuck in the system that got loosened up by all my poking around in there and by cycling the valve open/closed maybe I can 'clear the tracks' for good! Or at least til I need to replace the DCCV again. Seems to be on my yearly maintanence list now! At least I'm getting really good at it and could probably do it with my eyes closed! Actually, I can do it without looking, since you can't see anything burried in that STR engine bay anyway! lol

Thanks

 

So, looks like it all was just a sticking DCCV. Wife got home, didn't say anything about the climate control not working (she usually informs me of EVERY little thing that isn't right!), I got in the car to get gas (and yes I fill my wifes car up for her, since I don't get to drive it much anymore!) turned it on and guess what, cold air! Now, usually every time the car was shut off, you couldn't get cold air without some cycling of the temp controls. So, on the way to the gas station I cycled from LO to HI a bunch of times and everything worked perfect. Looks like some gunk or something got in the system (or possibly something to do with the valve itself) and was causing some sticking but all seems well now. I'll keep my eye on it and hopefully it won't happen again! I was thinking of taking the old DCCV apart and having a look to see if it can be rebuilt. Couldn't hurt to have an extra around! Thanks for all the advice, and still open to any ideas other than a sticky valve or ways to prevent it from sticking again if it decides to! I like when problems are something simple (hopefully) instead of a complete tear down of the car to fix.

 

Are you sure that your coolant level is at full capacity? And that all air has been bled out of the system?

 

I'm sure that the coolant is topped up (at the moment at least). I checked it two days ago, and will be checking it again. I usually keep an eye on it after I've had to drain and refill the system. There could be an air pocket still in there somewhere, but i have ran the car with the heat full at about 2000rpm for 15min or so at least twice since I refilled. Still a possibility, but I've never had air in there before as long as I run it like that after I fill. I will keep an eye on the coolant level and make sure it's topped up.

 

Good troubleshooting! I think you have it figured out.

Was the DCCV from Jaguar or the cheaper Lincoln LS version? They are supposed to be identical but with a few reports of new DCCV's failing or acting funny I wonder if there IS some kind of difference?
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Regardless of whether you purchase them from Jaguar, Lincoln, Ford, or rockauto.com, aren't they all a Bosch OEM part?

 

Well, all the DCCV's I've bought (three) plus the one that I took off the first time I changed it (that makes four!) have said Bosch on them. If I remember right, the first one I bought was listed as Jag OEM with the part number from a dealer site. The second two were listed under the Motorcraft part number (one from amazon, the other from ebay). In my opinion they are all made to the same (low) standard!

 

I have a faulty one, new one is a Bosch part. I also have a very similar one, faulty from a BMW. Yes, Bosch again....

I guess Bosch... cashing in on poor quality. grrrr

 

Bosch was well-respected as a provider of superb parts 25 years ago. Not so much now....