Dear all,

I've an issue with my heater on my 2003 Jaguar S-Type v8 4.2. The air is blowing colder on driver side than on passenger side. This happens when the heater must heat the cabin, whatever the temperature setting is, event in Hi mode.

I changed the DCCV, nothing changed. In the Hi position (not tested others), the 3 hoses going to the heater core are very very hot. To eliminate a RCCM cause, I unplug the fuse 32 which is powering the DCCV. As far as I understood, In this position, the DCCV let the coolant flows to the heater core. The hoses are still very very hot, but the problem remains.

I think that the DCCV and the RCCM are not responsible but may be I'm wrong. What can be the cause of this problem ?

Thank you,

Laurent

 

As the Brits may say, "Stop mucking about" and just go to Karl's Epic troubleshooting thread:
https://www.jaguarforums.com/forum/s...ol-how-185002/

 

Thank you Aholbro1.

I'll read your link carrefully and come back to this thread to let you know !

Laurent

 

Dear Laurent,

That's very good troubleshooting so far.

Something I would suggest is to get a clip-in pocket thermometer (to measure the actual vent temperature) and an infrared thermometer (to measure the heater lines under the hood).

When you selected manual HI, and with fuse F32 removed, that new DCCV should have spring-loaded open on both sides, as you tried. So this is very unusual that the one side is still cooler than the other. It's not very likely your new DCCV is bad, but that can't automatically be ruled out. Before trying anything else, please test the new DCCV as detailed here, in post #2:


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


I think it's very important to get an actual temperature reading at the ducts, and also at the heater lines. Perhaps the fault is actually an airflow problem, and thus one side doesn't feel as warm, but the temperature is the same. The thermometer will tell you.

To test the airflow, you could hold a piece of ribbon or yarn over the vent. Play with the fan speed and see if the airflow is the same on both sides.

Also, I wonder if the cabin air filter (at the base of the windshield on the left side) could be clogged. That might be restricting overall airflow, and perhaps that's enough to make one side a bit stronger than the other.

 

Laurent,

One more thought in favor of an accurate reading from an infrared thermometer: Let's say for reasons still unknown, there is 40F difference in the two smaller heater lines. Remember, the two smaller lines each feed one side of the heater core, and the larger line is the common return. Both are going to feel extremely hot, yet one side might only be 160F versus 200F on the other side. To the bare hand, you'd be trying to discern the difference between "Ouch! Ouch! Ouch!" and "Ouch! Ouch! Ouch! Ouch!".

If nothing else, an infrared thermometer makes a great toy. Many inexpensive models are now available these days, so you don't have to spend a lot of money.

Keep us posted.

 

Hello kr98664,

thank you for your answers. I've just ordered 2 thermometers, one infrared and one with a probe to check the temperatures.

I'll keep you up !

Laurent

 

All,

I performed some temperature measurements on the hoses of the heater. So, the results are weird :
- close to the firewall, I got 78C (172F) on one hose and 65 (149F) on the other (metallic hose) ;
- close to the junction between the metallic hose and the rubber hose (just after the DCCV), I got 78C (172F) on both !

So I followed the metallic hose with the infrared thermometer and nearly 10cm (3,9"), after the junction, the temperature fell ! Like if the hose was clogged ... Weird isnt-it ? I touched the hose with my finger and I did not detect any anomaly (but it was host and I did not insist) Is it possible that the hose is clogged ? Or is-it an error when I gauged the temperature ?

Thanks,

Laurent

 

Enjoying that infrared thermometer yet? Thanks for humoring me and getting one. As you have already seen, they are amazing for troubleshooting. If your readings are correct, it sounds like you are hot on the trail.

Before tearing anything apart, I'd suggest repeating your findings. I forgot to mention these thermometers can be a little finicky sometimes. The infrared energy needs to reflect back to the gun. The most accurate readings are obtained straight on. If the measured surface angles away, less energy returns to the gun, and accuracy drops off. So play with different angles, and see how that affects your accuracy.

Also, the material affects the reading, too. A rubber hose (less reflective) usually reads lower than a metal line (more reflective). When taking comparative readings between two points, check metal vs. metal or rubber vs. rubber, instead of mixing them up. I don't care to discuss how I learned this... Anyways, it sounds like you are already doing it correctly, but I just wanted to be sure.

The point where the temperature drops within the heater line: Is that rubber or metal?

If rubber, I wonder if the hose has delaminated internally and created a blockage. I've had this happen on brake lines, and everything looked fine on the outside.

If metal, that would point to some kind of debris blocking the path. However, this doesn't seem very likely, but who knows. My HVAC troubleshooting guide has a picture showing a severely clogged DCCV, for example. When you replaced the old DCCV, was there any crud like that? Also, is there a sharp bend at the suspected clog location? A sharp bend would be more likely to catch any crud, as compared to a straight run.

 

Hello all,

some months (years ?) after this post, my dccv died again. I changed it and I tried to figure out this issue with the heater. I found it ! The heater core seems clogged. I removed the 3 hoses and tried to blow into the inlet hoses. It was easy in the passenger inlet but hard in the driver one which confirm the temperature difference between driver and passenger side.

I connected a garden hose to force water into the heater core without success. I put metal 5 for cleaning the coolant system directly in the heater core without success. What can I do now to try to unclog the eater core (everything is reassembled now) ? Is-it easy to change it ?

Thanks,

Laurent

 

Where did you disconnect the hoses? At the DCCV or at the firewall? If disconnected at the DCCV, you'd also be trying to blow through the hoses. Before even THINKING about changing the heater core, I'd want to be triple positive the hoses are not the source of the restriction.

Where did you connect the garden hose? On the two smaller supply lines, or the larger return line? If you haven't done so already, try connecting the hose to the return line. That would reverse the normal flow and hopefully dislodge any clog inside the heater core. If you connected the garden hose to the supply lines, that would force any clog deeper into the core, so reverse flow is good.

How much of a temperature difference are you seeing between the two sides? If not too much, I'd be tempted to just live with it. From what I understand, it is a HUGE job to replace the heater core. I have visions that the heater core was the first part down the assembly line and the car was built around it.

 

Thanks kr98664 for you answer. So I disconnect the hoses at the firewall level and I connected the garden hose on the return (the big line) and I blocked the passenger outlet to get all the stream going thought the driver circuit. The difference is nearly 15C (122F on driver side and 150F on the passenger side).

"I have visions that the heater core was the first part down the assembly line and the car was built around it." => LOL :-)

Laurent

 

"I have visions that the heater core was the first part down the assembly line and the car was built around it." => LOL :-)

Your vision is not necessarily all that wrong...