greetings to all

I am the new owner of a 1994 Jaguar xjs. Car runs and looks great. The problem here is that their is no heat. The air conditioning blows cold, cold, cold. That is fine on a hot day but not good for a cool evening. I am being told that if its the module no one will service it. I was basically told by a reputable tech. and owner of the company their was nothing he could do. Am I stuck with a car that can not be heated. Great if I lived in Florida but terrible for New England. Thanks in advance for any help.

 

kenxjs,

A good XJS specialist would be able to do some very simple basic tests and start to pinpoint the problem. I'm also not sure what the "reputable tech" means by the "module", That's not a term that we recognise for your car.

One simple test you can do is check whether the heater control valve is opening. I'm guessing that you have a 4 litre XJS? (It would be helpful to update your signature). If so, it's at the back top of the engine on the left hand side. Just google "Jaguar XJS heater control valve" and you'll see what you're looking for. Set the heating to hot and then see if there is heat in the pipes on either side of the valve, That's your first simple test.

Good luck

Paul

 

Which is code for "We don't want to be bothered with this car or this problem".

As mentioned, the heater valve is easy to check and, if faulty, easy to replace.

The climate control system can be tricky, yes, but some of the fixes are actually easy. Broken vacuum hoses, dirty connectors, poor electrical grounds. But, it does take time and patience to deal with these things. At present-day shop rates the bill grow quickly.

Cheers
DD

 

Paul and Doug,
thanks for your replies. I am new to the Jaguar world. I have owned an MGB for several years and am quite adept at working on them. I have owned this new 1994 Jaguar XJS for about 10 days so I'm not sure about all of the terminology, yes it is a 4 litre. I took it on a 1,400 mile journey since owning it. The outside temperature was in the high 40's to low 50's. The person I bought it from was telling me how well the air-conditioning worked, he was right. The thing is we were quite cold with the low temps outside. I was told by the tech that if this thing, some computer or control did not work properly there was no one who services them and there was nothing he could do. I have it scheduled for service in early June with a place that works exclusively on Jaguars . That was the earliest date available. I am looking into this problem and trying to see if I can fix it myself. A jaguar is not an MG that is for sure. This car is in mint condition with only 30,000 miles on it. I will look for broken vacuum hoses and the heater valve as suggested. thanks much!

 

You have a Delanair Mark III system, and it uses two drums as blend doors and directs air to appropriate vents. Assuming the heater valve passes the test, and you do have hot coolant circulating to the heater core, then try setting the system to defrost. Do you get air out the appropriate vent at the windshield, and none at the dash vents? If you set the temperature control to full heat, do you get air at the floor and none at the dash vents? When set to full cold do you get air at the dash vents only? It can take a while for the system to react, so be patient. Report back on the results of those test and we can guide you further.

A quick test of the heater valve on the firewall is it is normally open and closes with the application of vacuum. So you can test by pulling off the vacuum line and plugging it, the heater valve should be open. If you have a hand vacuum pump you can test it, you should be able to see the arm move to open the valve.

 

thanks to all who have replied. This attached video describes the problem similarly. The only difference is that he says he gets lukewarm air at best. I was told by the reputable tech and owner of the company (that works on Jaguars exclusively) that if the Climate Control Module was the problem that there was nothing he could do. The part is not available and that no one could service it or fix it. If this be the case I will find this car very unusable as I will always be cold. As I mentioned earlier we took an extended trip and were driving with jackets on. what to do when it gets colder?
This could be an excellent car for Florida, not New England.

 

And it may very well be the case the the module is on the fritz.

Or not.

I'm under the impression, perhaps incorrectly, that this technician has never actually put his hands on your car. Until/unless you say that this fellow actually spent some time investigating the problem I would not put too much credence in his remarks. There are several possible faults that could cause a 'no heat' symptom.

And....even if the module is proven faulty has he shopped around for a good used module to replace it?

Cheers
DD

 

Thanks Doug,

I like what you say and will hope for the best. I checked today and it seems the heater valve is working fine (both sides hot?) The vacuum line was clean. I have a service scheduled for June 2. I will give a full report. And of course I still welcome other comments. thanks again

 

I would listen carefully to Doug. I think this shop is trying to subtly tell you they don't want the business. The module being bad isn't a "nothing I can do with it" situation. Used modules are available on Ebay fairly cheaply and swapping one out isn't rocket science.

Given that the car only has 30K, it could be something as simple as a stuck blend flaps (the XJS doesn't appreciate being neglected). It will get expensive if you have someone start throwing parts at it without an intelligent series of tests to pinpoint the problem. Though the XJS seems complex, it isn't as much as you would think once you get stuck in, and it sounds like you might have the skills to solve this on your own. I have to warn you though, once you solve a problem on the XJS it sort of gets its claws into you and increases your affection for the beast. Lots of friendly help here to assist you as you need it.

Cheers

 

I have seen more than one dead blend door motor, so that's what I was asking about the position of air and temperature. There are two blend door motors, and together they control both the temperature and where the air comes out. Knowing how the systems responds can narrow it down to one, both or none of the blend doors motors being faulty.

Here are the positions, the top is full cold, the bottom is full heat.

 

I have what I believe is the MkII system in my 1986. I've owned the car for a year. Over that past year it's seemed like the heat/AC/ climate control has a mind of it's own. Until recently it's always eventually done what I asked it to do until recently. The heat has stopped all together now. I was on my way to the shop on a cool morning and could not get the heat to change over from AC. I was told by the mechanic at the shop that the units that controlled the temperature were at best temperamental and also expensive to obtain ($800) and then more often than not would fail again before too long. He advised me to have him set it so the AC would stay on since the car would be driven mostly in the summer in fair weather. I am thinking he forgot to do that. Last weekend I was out for a drive and the AC was on low blowing out the center vent when it stopped and started coming out the vents on either side of the console where the heat would normally exit. Still cold. I found this write up by Doug and I am going to look into this myself at it when I get a chance.

https://www.jaguarforums.com/forum/x...basics-178059/

Good luck sorting yours!

 

Classic symptoms of a duff amplifer and/or duff regulator unit. talk to Jag-Aire and do their tests, and they will supply the parts you need at a very fair cost.
https://www.jag-aire.com/

 

Thanks for that link!

 

I was wondering how easily accessible this part is?

Dash off or Stereo out?

Or seats out and an "On yer back" route?

Gee.

 

The lower servo motor is reasonably easy to access. The lower vent trim panel comes off, and then the ECU is removed. It's only held on with a couple of screws.

The upper motor is much more difficult, that's steering wheel out, air bags out, and entire dash assembly out to access. Naturally, that's what was faulty on my car.

 

Sure enough the mechanic didn't touch it! Saturday went for a drive and the heat was working! Then I set the controls for the A/C to come on, and lo and behold it did. We'll see what happens next, but I will check electrical connections next.

 

thanks, it's a work in progress

 

I also have a no heat issue from the footwell vents. I have done a number of fault finding tests and the system seems to be fine except for the lower servo motor. I am only getting cold air from these vents. I have a good used servo motor, but I need some guidance on how to remove the original one. I have removed the vent panel, the black metal duct, and the ECU. I can't quite reach the servo motor itself. Does anyone know how much of the dash I have to remove? It would be nice to get the Delanaire III working properly.
Thanks for any help!

 

There are two screws holding the motor to the heater case, I think that once you have the ECU out they should be visible. Unplug the motor, remove the screws and it should pull out. It's been a while, but I recall changing the lower motor by only removing the lower console panel. If you were able to remove the ECU, you should be 99% of the way there.

 

Here is a photo of when I changed my upper, but the lower is the only visible motor, and the ECU is the brown plastic hanging at the bottom of the photo.