Hey all. My jag has no heat. But does have heat when the ac pump is unplugged and has no power to it. Have noticed that what looks like the HVC has been by passed for some odd reason. Could this be my problem? Or sence its english is there more to this problem? Got all summer to sort it out but of course sooner is better cause I do actually enjoy working on this car.

 

if you search out one of my old threads, called 'A/C Dazed and confused' you will find some very usefull links and comments that could be of help. I had a different problem to yours, but the info should be of some help.
Cheers
Richard

 

Well I did some of the reading on yours an it sorry to say is.none of. The problems I'm having. As I have cold air when when the ac pump is plugged in. And warm air when it's not plugged in.

 

Ok, I will rephrase what I meant.

In my old thread, there are some links to how the system works. My problem was different, but I suspect that your problem is related to similar issues. I don't know what system you have (don't know what Jag you have).

If you have the delenair mark 2 system then my suspicions are one of the following:

* A/C amplifier has failed

* There is a problem in the vacuum hoses somewhere

* The temperature knob is not working (my thread has instructions in there somewhere on how to test this)

* worst case scenario (like mine is) is the servo unit is sick. It is buried waaaay in the guts of the dash.


What is happening is that when the compressor is connected, it is getting the signal to make, and produce cold air. the good news here is that your a/c is holding its gas, and that the cooling works well.

There is also the possibility that the clutch on the compressor is seized in the engaged position.

I am not an expert, but have had a lot of advice from the experts on here. I would suggest reading the whole thread, and also looking at the links, as they do illustrate how the system works.

Mind you, if your system is an older one installed by a dealer, then ignore all of what I have said, and put some more details so others can help. There are many people on here that know (and probably dread) the a/c systems, and will probably add some more details when the time zones align.

Cheers,
Richard

 

Quite possibly something simple like your heater tap might be jammed in a partially open position, allowing heat to pass through the heater core and blow warm air when the A/C is off, but when you have the cold A/C turned on, it chills the air enough to make a noticeable difference.


Then there is the blend door, that could be stuck as well, not diverting or blocking the hot air off.


A vacuum line could be deteriorated or fallen off that controls a swing door or tap operation.

 

Actual heated air? or, simply air that is ambient temperature and not refrigerated?

The system is designed so that all incoming air is chilled first and then heated as required. Unplugging the compressor obviously means that the incoming air cannot be chilled.






HVC = heater control valve?

If so, how was it bypassed? Do you mean the two hot water hoses are not connected to it? Or do you mean the vacuum hose has been disconnected?

A disconnected vacuum hose would keep the heater control valve open at all times....thus allowing hot water/coolant to flow into the heater core. If the hot water hoses are attached, of course. If the hot water hoses are not attached to the heater control valve then the heater will not work because not hot water is flowing into the heater core.

When you turn the temp dial to max heat, what happens to the airflow? Does almost all the air come from the footwell outlets? If so, that's a good sign....as the system at least understands the request for heating. If not, describe what happens.


Cheers
DD

 

replace the heater valve.

if it has been bypassed, then of course you will not have any heat ever.