Love my 1999 XJ8. New to this forum and this is my first post. Last 2 years have had heater issues. Last March, no heat. I had the heater core flushed out and it seemed to work. This year, the first cold day, no heat. I was told the heater valve was fried and spent over $600 to fix. Picked up the car and no heat. The shop told me it was working great the day before. Car back in the shop now and they seem to have problems figuring it out. They even tried a new climate control module and didn't help. Anyone have had similar problems or thoughts. Thanks.

 

To clarify....

No heat at all, ever? Or not very much heat when you're expecting lots of heat?

If the latter you might want to look at the other heater thread in this section.

If the former, have they checked the heater pump? Is the engine reaching normal operating temperature?

Cheers
DD

 

Have them read these.

 

My first suspicion is that the auxiliary heater pump has died. It's probably consumed its brushes.

I cannot believe that any Jag shop wouldn't look at this as a first item in a "no heat" situation. Now that the cars have reached "a certain age" this is an incredibly common cause of no heat.

 

Thanks for your reply. No heat at all, even when the engine has heated up. The shop told me that there was a lot of heat right after they fixed it, but now getting heat intermittently.

 

Do you get heat if you select Hi with the engine at normal temp?....worth a test, some of us see this .......it's strange....we are tryingh to get to the bottom of it......Allan

 

If the "octopus" is original, I would recommend checking the one-way valves.

Bill

 

I've been watching these heater threads with interest. My heater doesn't work very well either. I thought I would make a project out of replacing the brushes on the heater pump, and I did. No difference. The brushes were worn down, but still working I think. The heater valve looks intimidating, as does the octopus. I didn't touch them, yet anyway, other than what was necessary to get the pump motor out. If I turn the A/C off and move the vents to where it will warm my frozen hands, it will give me some warmth. The heated seats help some. They don't get toasty either though. I'll have to pull the codes. That was a very nice thing to have - the PDF docs for the climate control. My old Land Rover will bake you pretty quick, unlike the Jag.

 

Jimmy there is a fix for the seats- https://www.jaguarforums.com/forum/x...-solved-44965/

 

Thanks. Took it back to my mechanic. He thinks the venting beneath the dash which redirects hot air/ AC, etc is the problem and will have to take apart the dash. I don't have great technical understanding of the specific mechanicals in this car, but is this what you are referring to as the "octopus"?

 

No, the octopus is a cluster of hoses between the heater pump, the heater switch, and whatever else it goes to, but it's made up of coolant hoses under the hood. I understand it has a couple of one way valves included in it too. It's situated under the coolant header tank. I dunno about taking apart the dash. That sounds like mechanic needs money for Christmas gifts.

 

The system is designed so that incoming air is first refrigerated and dehumidified and then heated as required. This is accomplished by internal flaps that direct the refrigerated air *through* the heater core (when heat is called for) or *around* the heater core (when cooling is called for).

I suspect that what I call "internal flaps" might be what your mechanic calls "the venting beneath the dash which redirects hot air/ AC".

If the common and easier-to-fix suspects (pump, hoses... heater valve already replaced) have postively been eliminated then I'd be reluctant to condem his course of investigation. It seems plausible.

Cheers
DD

 

I didn't think that *anyone* else did the Rube Goldberg configuration that is also shared by Rolls-Royce, at least, as far as "cooling before heating" goes. They've been doing that for decades, but only if the ambient outdoor temperature is somewhat above freezing.

I absolutely agree with what you've written, but want to add that there should be a huge emphasis on that If. The dashes in these cars were "drop-in" pre-assembled units and don't lend themselves to being taken apart and put back together again. It's one of those "it'll never be the same" situations.

I'd also make sure that all checks of the actuators, cables, etc., that can be done without taking anything apart (other than, perhaps, your neck and back muscles) be done as well before you even consider disassembling the dashboard.

Check all of the "usual suspects" plus anything else you can check before you resort to taking the dash apart.

 

I think it's probably more common than we think on "climate control" type systems







I agree on emphasizing the "IF" part :-)

I've never delved into the HVAC on the X300 cars specifically but I remember doing some other repairs and it seemed like at least some of the HVAC stuff was fairly easily accessible under there.

It's common for repair shops to be a little dramatic. "The whole dashboard has to come out of the car" or "we gotta tear apart the ENTIRE dashboard" or similar.

Yeah, maybe for an evap core replacement or in some cases a heater core replacement....but not for all HVAC repairs by any means.

Removing the glove box and a few trim panels and the air bag module etc. isn't all that big of a thing.

But, yeah, if you reach the point where you have to work *inside* the main HVAC case then things can get pretty hairy




I agree.

Cheers
DD

 

My mechanic thinks the problem is in the blower case. He thinks the door between the heater box and A/C evaporator is either not closing all the way or the sealing foam on the doors has deteriorated. He says that when the unit is not on "auto" mode, it is getting heat. I guess that if it is off auto mode, the evaporator is not cold and no cold air gets in. They ran a fiber optic cable down the docts and the blend door that separates the the a/c and heat is binding 1/2 to 3/4 inch allowing cold air into the ducts. I don't have the car back, but hopefully I can get heat into the car in non auto mode.

 

I hope I'm wrong, but while you may get heat the amount of that heat is going to be highly dependent on what the ambient outside temperature happens to be.

You are right that when not in Auto mode the AC compressor does not operate (let's ignore if you turn on defrost/defog - then it does). However, if the blend door is binding as you describe you will end up with both a ram supply of outdoor air plus it being picked up and blown out by the fans. If it's not frigid outside the heater should be easily able to overcome this if you set the temperature up high enough that the heater core has a good supply of hot water. If it is frigid outside, though, that gives the heating system just as much to overcome as it has when the AC is pre-chilling/dehumidifying the incoming air.

 

I think I have this issue.