Noticed that I have a heating problem with my 2000 S-Type. All summer long the A/C worked flawlessly and without issue, but yesterday minimal heat on the driver’s side. I went out today and did a little checking. With the car at operating temperature I found the hoses from the DCCV were about 10° +/- a few difference between each other with the system on manual and both sides set on the same temperature. I went inside and found the same 10° to 14° difference between the driver’s and passenger’s side. I then turned on the defroster and I see the same temperature difference. I am going to go out in the morning to make a few more checks but all this is leading me to the DCCV valve. On the onset I thought it might be the evaporator temperature sensor (ETS) but I am now thinking the DCCV because I think (not sure) the ETS is out of the picture when the defrost is turned on.

Any input would be appreciated.

 

Jeeesh Gus, you're asking us for help

Its a bad day and time to close the forum, as you pretty much have most if not all the answers.

I hope someone somewhere can chime in and offer you some help for a change!!

Good luck Gus

 

I can find info on low A/C but little about no heat.

 

I'd say that the DCCV would be a good bet, is the only thing that could give you different temps on each hose.
If you are at max temp I don't think the sensors have any effect.
I just took mine out and cleaned them, if the 2000 is the same arrangement you need to be a bit of a contortionist to get to the drivers side ones.

 

Try here to check DCCV DIY: Diagnose It Yourself - JaguarClimateControl.com it may help

 

Yes I have seen this and it has a lot of information but it is geared towards A/C and not so much heat. Thanks!

 

Wish I could add something helpful Gus. I haven't had to deal with any heat problems thus far, so I am an idiot on the subject .

I do agree though, the DCCV is the likely culprit.

 

Changing the DCCV fixed my lackluster heat. There was some heat coming by manipulating the controls last winter, but the car never tried to heat itself like it should in auto mode once the engine is hot.

Not urgent due to moderate climate, but I changed the DCCV over the summer knowing that DCCVs fail and coolant change seemed like a perfect opportunity.

Now that cool weather has returned the heating works as I remember it should. I did open the old DCCV and the valves did not seem stuck, but very little (< 1-2mm) movement on them.

 

GUS does your have an auxillary pump for the heater, could it be that?

 

Hello all,

just a quick update on a recent fault i have had. Despite all the other fault diagnosis available for the above, i have a new one for you.

After stripping the car to the bare bones, yet again a poor wiring harness issue has appeared on the STR.

Heavily corroded wires within the cars main wiring harness upfront have taken out the Remote Climate Control Module. My tech has had to strip the car down to find the corroded wires, repair/replace and re-sheath the harness to keep water tight and fit and programme a new RCCM.

We had the dash out, matrix checked and flushed all pipes checked, aux heater pump checked, dccv checked and the b******y dodgy s type wiring was at fault again. Second wiring harness it has had, first one screwed the gearbox at only 60K.

Hopefully this info will be assistance and help to others in the future....

 

A little trick I learned from my mechanic.... if the coolant is low or below the minimum mark on the coolant tank, heating will not work properly.

 

Did a little troubleshooting this morning and so far no conclusion but still gathering information.

I took the car out for a run to get it to operating temperature. On the way out it seemed I had the same temperature out of both face vents and both were the same for a while, but not the entire time. When I got back I checked the temperature inside and I had a 15° difference between the left and right vent. Under the hood I checked all 3 hoses going into the firewall of the car. The 2 smaller ones leaving the DCCV were within 2° difference of each other. The bottom hose I think is the return was 3° lower. I should mention I took the average of 5 temperature readings on each line to make sure I was on track, what I need to know now is the line designation going into the firewall. The temperature being near the same on both hoses leaving the DCCV leads me to believe that I have flow on both valves. The question is why I do not have it in the car.

 

The 3.0 is without a pump. Thanks!

 

This is what a broken s type with faulty wiring harness and no heat fault looks like...

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My eyes! My eyes! You know how to make a guy feel good.

 

Just got back from a drive, as the car warms up I can feel warm air from both vents but when the car reaches operation temperature the driver’s side gets cold. After the car was sitting for about 1-2hrs started it up and I got warm air out of both sides for about a mile then the driver’s side went cold again. I am thinking the temp. sensor.

 

Hi Gus!

Now that I've had a moment to review and digest your heater issue, I think I have the scenario that will play out.

What you describe is indicative of a restriction in the flow of coolant to the heater matrix. That could be caused by a failure of the DCCV, plugging of the matrix or disintegration and collapse of a hose to the matrix. I don't think your car is old enough, or in a degraded enough condition to suggest the hose problem. I suspect the DCCV is either restricted due to a build up or a solenoid that has stuck partially closed.

The easiest way to decide if it is a control problem or a restriction is to simply disconnect the DCCV electrical connector. The valve defaults to fully open when relaxed and not energized. It is energized to shut off the coolant flow for air conditioning. With it disconnected you SHOULD be stuck with full heat; if you still have the cooldown on one side, you know it has to be a flow reduction to that side of the matrix. [that would rule out the temp sensor, for instance]

The scenario I was referring to is how I've learned to present this to owners. I tell them we need to start by repairing the DCCV and then reassess. Once the DCCV is corrected, there may still be a flow issue to some degree with the matrix, it's about a 50/50 crap shoot. If you have full heat, you are good to go; if not, it's time to go after the matrix.

So, unhook your valve and see what happens.

Good luck!

 

It should be easy and cheap if somewhat of a faff to check the temp sensors as they are thermistors and should all have the same or very similar readings, to check the heater core is it possible to remove the feed and return hose and then check by pouring water through to see if the matrix is blocked or is that not possible?

 

Both are possible Barney, but faff doesn't begin to describe the PIA of getting those sensors out.
Disconnecting the valve is a 5 minute job which should separate a control or restriction problem without spilling coolant.
Incidentally when I had my sensors out I had no idea what the correct resistance should be, but they all showed the same, I put them in the freezer for a few minutes and checked again, the still showed equal (higher) resistance and quickly returned to the original (ambient) value so i assumed they were good. As others have mentioned the sensor behind the small grille over the ignition key had a good coating of fluff on it.

 

when you disconnected the valve did the heater run hot?