Cordial Greetings,

After digging through the archives, I've come up with a plan of attack for a no-heat condition in my '02 S-Type. With some semi-educated guesswork, I suspect the climate control thinks it's putting out warm air when it really isn't. I'd appreciate any comments or suggestions.

This is a first time for anything like this. Not sure how long it's been happening, could be up to a couple of months, since little or no heat was required during the summer months. More likely just a week or two, since most mornings the ambient temp has been in the upper 50s during my morning commute (Oregon).

The symptoms:

1) No heat with the climate control in auto mode.

2) Flame-thrower like heat when manually set to HI.

3) When in auto mode, the outlet air is approximately 35 degrees. (Measured with a thermometer in the central dash vent.)

4) With A/C button off, the outlet air is close to ambient.

5) Selecting the various outlet buttons (across the bottom of the panel) has no effect on the temperature.

6) Adjusting the temperature side-to-side has no effect on the outlet temperature.

7) If the interior is already hot (i.e. parked in the sun), the controller automatically puts the A/C system in recirc mode for a while as it is designed to do. When the interior is cold, this does not happen (also as designed). More on this below.


Because I've got LOTS of heat when manually set to HI, I don't believe there's any problem with the heater core itself. Also, I don't believe the DCCV is at fault, since it routes hot coolant to the heater core when manual mode is selected. That suggests the controller's output circuit to the DCCV is intact and functioning correctly.

My hunch is one of the 3 evaporator temp sensors has gone bad and is supplying a false high temp signal, fooling the controller into thinking it's already putting out warm air. I've got 3 sensors on order from my local Ford dealer and will pick them up this afternoon.

I will also clean the in-cabin temp sensor (above the ignition switch). This is free and doesn't hurt anything even if not needed, but I don't think this is the problem. See symptom #7 above. My thoughts are if the in-cabin temp sensor was falsely signalling a hot interior (and thus max cooling), the A/C would also kick into recirc mode.

The DCCV was replaced about 3 years ago (with a genuine Jag part) due to an external leak. It's worked fine since then, with no climate control issues.

The only other thing I've noticed is if the coolant level drops a little, the heat output drops at idle, but is fine at road speeds. However, it's done this since I've owned the car (5 years), so this is not new. It's such a minor issue, I've never done anything about it other to make sure the coolant level is correct, which takes care of the problem.

Any thoughts?

 

Worth checking what LO setting does, but especially see the - JaguarClimateControl.com site

 

My initial thought is the CCM is faulty...

 

LO setting works as designed, super cold air at max fan speed. I cycled the settings a few times from LO to HI, but no change.

I did notice one more thing this morning. If I bumped the setting from HI down to 85 or 84, the heater output was comparable to what I'd have expected to see if I'd selected my normal 72ish, i.e. moderate duct temp and low fan speed. If I dropped the selection to 83 or 82, the duct temp went to full cold and the fan went to full high.

Reading through JaguarClimateControl.com, I've had to extrapolate somewhat as that info seems to be mostly geared towards the '03-'08 models with the newer dash. On the diagnostics page, near the bottom under "Other Symptoms", Symptom #1 sounds almost exactly like what I have, and points to one or more of the 3 evaporator discharge temp sensors.

I hope to have some time this evening to work on the car. As I want to limit my time crawling on the floor, I may first read out the sensor values from the module connector and see what I have.

 

Why are you losing coolant? That should not be a regular problem or else you have a leak?
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Much happiness to report! I swapped out the three evap temp sensors. Not much fun to crawl under the dash, but I had all three done in about 20 minutes.

A quick reading showed the three new sensors and two of the old sensors read about 31k ohms at 70 degrees F. The third old sensor showed only 7k ohms, which corresponds to well over 100F on a properly functioning sensor. This was the upper sensor on the left side.

Went for a quick test ride last night, but the outside air was too warm for the system to command much heat, so I waited for this morning for a proper verification. I know it worked because I got distracted and forgot all about the heater output until I was almost to work, which means it worked perfectly at a nice moderate temperature.

I am one happy camper.

 

Well fixed. I will change my sensors now. 20 minutes sounds almost fast. Where did you get the new sensors? Thanks Paul

 

Hi Paul,

I got the sensors from my local Ford dealer. They were $20.20 each, but that is with a discount I get through my employer. Apparently these sensors are used in many Ford vehicles.

I simply called and gave them the Ford number I found on other threads here. The dealer had them for me the next day:

XW4Z-19C734-BA

That number is cast into the sensor body. The Ford box also had this number:

Motorcraft YH1504

If you're not in a hurry, I found dozens of online vendors offering the part. I had better luck searching with the Motorcraft part number. The sensors are also available in aftermarket brands, but I preferred the genuine Ford version.

 

Good!
You didn't change the one that's also a humidity sensor and presumably must have another part #?

 

That's correct. If I understand the system correctly, the sensor above the ignition key is a combo temp/humidity sensor for the cabin. Per some other posts, this is a Jaguar-only part. I didn't touch this sensor, and even forgot to clean it as planned.

 

OK, thanks. Thanks as well for posting the Ford part. Hopefully I'll never need it but thanks again if I do!

 

Update for anybody who comes across this old thread. I had the nomenclature wrong for the three sensors.

I had called all three of them evaporator temperatures sensors. Only one is called that. The other two are the left and right discharge duct temperature sensors. Sorry for any confusion.

More details and pictures here, specifically post #3:

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