My current Jag, 2005 S-type is my first one. Yesterday the air coming from the air conditioner started to blow hot air from the two driver side vents. The two passenger vents are still blowing cool air. Does anyone know why? Does it not all come from the same air conditioner?

 

The S-Type has dual climate control system, allowing different temp settings for the driver and passenger. There is a dual heater control valve, which sits below your coolant resevior. When the coolant resevior leaks, it leaks directly onto the valve, then causes the valve to short out, and usually takes out the control module as well.


However, there is a way to fix this without replacing the module. You will most likely need a new dual heater control valve, which is a bosch part, so you don't need to go to the dealer for it. The control module will require some disassembly on your part, unless you're not comfortable with doing that, and if you have a local tech you can take it to, they should be able to sort it for you. I believe there are some pictures on the forum relating to this exact fault, so you can see where the fault lies in the circuit board.


I have also seen on rare occasions that low Freon can cause a similar symptom, but most likely its your dual heater control valve.

 

RebelMan you get points for admitting you have a 2005 S-type, but also demerits for not telling us whether it is the 3.0L or the 4.2L!

JB is probably correct, but you really ought follow a methodical test regimen to determine what has actually failed. Lots of threads here on it; search "DCCV" or try "Climate Control" or even "hot air" and you'll find lots of fun reading material.

Buy the valve from Bosch or Four Seasons if you want to become an expert at changing them. Try Motorcraft if you'd like to change it and be done with it for a few years.

 

+1. Hahaha . . . gosh that was subtle . . . sorta like a runaway, out of control freight train. Well done Zane, and I almost missed it . . . not!
LOL

Cheers,

Ken

 

I've come to the conclusion that this AC system was a design nightmare right out of the gate.. A year ago I had this gremlin appear in my 2005 4.2 .. I did my due diligence and researched the threads. I ordered a NEW Bosh DCC valve and had it replaced, Then I sent off the climate control module that had the trace's burnt out. That got fixed, and everything worked great for a while .... Now that summer has started, the darn thing is acting up again... When my car is parked in a garage, or a covered parking structure with shade, the AC will work and keep the car super cool once I start rolling around town... HOWEVER, if I leave my car in a regular parking lot where the car gets a lot of sun, the AC will NEVER recover.... I can't figure it out... Its not like the thing don't work, because under the right conditions it works great, but the second you park in the hot sun and shut the car off, BAM you have hot air blowing and the AC never recovers once you start it back up after its been sitting for an hour or so .

 

There's a TSB explaining to swap a spring and valve or some such to improve idle/low speed performance. I know it applied to the 3.0L's....don't recall about the 4.2L.

Do you get cold air (45-50F) out of the registers at speed?
Also in play, if your car is black or some other dark color, particularly with a dark interior, you have a lot of ground to make up after a hot-soak...but still, it should be as good as it once was...

 

my car is black, 4.2 with a light interior ... I'm not sure what the issue is, but it blows out hot air no question about it... I honestly think I got a bad DCC valve... I have ruled out the CCM because sometimes the cold air works great... like I said, if I pull out of the garage in the heat of the day and my car has been sitting in my cool garage, the AC works GREAT ...

 

Not sure about the 4.2L, but with a 3.0L, if you set the climate control to "Lo" you'll get cool air out of the center vents (although hot out of outboard and rear seat console) even with a knackered water valve. 4.2L, with aux elec. pump...may move more water, so that may not be true for it.

If it IS your valve (and let's be honest, you have the Bosch, so it is likely) you should have cold air after any cold-start, for a few minutes, however brief. Now, if you have been soaking in the sun, that cool air may be wasted cooling down the HVAC case, ducts, and ventworks before it gets to where you can feel it, and is then warm. I had one that would randomly fail open - so everything would be fine for 30 min, or 5 min, then hot air everywhere.

So if you leave from your cool garage, with A/C working great...does it always and forevermore work great until you park it in the sunshine and come back to it? Or if you hit stoplights, does it start failing? Or just randomly go hot at some point?

A DCCV that is leaking internally (letting a little coolant past the "closed" valve into the heater core) may present as substandard a/c performance. But one that is stuck open, or open when not commanded, is fairly easy to divine from the cabin. As noted before, the only way I could tolerate it on even a mild day was to close outboard and rear vents, turn blower to hi and temp to lo, then enjoy the somewhat cool air from the center two.

If you find yourself enjoying nice cold air at speed, but suffocating at idle, it is time to check the operation of your radiator cooling fans.

 

when I leave from my garage, as long as I don't turn off my car and let it sit in the hot sun it will stay cold... Ive driven for hours with it not having an issue... Its only when its been sitting in the hot sun... I can drive in the hot sun all day with COLD air as long as I'm starting from my garage.. The minuet I turn the car off and let it sit I'm screwed ...

 

Only thing I can come up with would be a faulty cabin air temp sensor, then. Above a certain temp, it fails to a value corresponding to "Cold" making the HVAC think everything needs to be warmed up. You could watch it and see what it is reporting on WDS if you have it available. Maybe try cleaning it out? But even with that, if you set the temp to Full Cold or "Lo" it should disregard all the temp sensors and close the water valve, turn the fan on high and open the Fresh/Recirc door to Recirc.

 

+1 on that. I was just about to compose a reply suggesting the exact same thing. Only his reply (quoted above) is clear, to the point, and only one paragraph long...

 

I'll give that a go.... I did have it set to lo , but I will try the resirc and see what happens, If I recall, I believe I did get it to work once or twice by playing with the recirc ... Are these temp sensors hard to replace ?

 

OK....but just setting your temp to Lo should illuminate the recirc light on the button, indicating the door is in recirc position. THere is a limited number of minutes it will stay there, unless you hold the button down >2 sec and get a "beep" in which case it should remain in Recirc until the next key-off evolution.

 

The EVAP temp sensor has been a fairly common issue, you can check codes to see if you get a code B1946/B1947 logged in Climate Control module. These usually indicate a faulty EVAP temp sensor, and will cause the A/C to blow warm, across the whole dash, not just one side.

 

Setting the temp to LO puts the system in manual mode and bypasses most of the automatic controls. From what I understand, however, the evaporator discharge sensor is still in the circuit. Even in manual, it's used to control the compressor by inferring low side refrigerant pressure. Unlike most AC systems, there is no pressure sensor or cutout switch on the low side. Read this thread for more details:

https://www.jaguarforums.com/forum/s...c-help-148484/

As detailed in that link, that same sensor is used in two other places. You can take a resistance reading of all three by unplugging the CCM. At 70F, you should see about 31k ohms of resistance across each one.

My HunchDuJour™ is the evaporator sensor fails when the car bakes in the sun but unfortunately gives a false signal that won't let the compressor run long enough to cool down.

Post #36 in this thread has more details about the sensors:

https://www.jaguarforums.com/forum/s...r-35014/page2/

 

The Evap temp sensor defaults to 32F, which is freezing, in turn shuts the compressor off to prevent the EVAP core from freezing over.