Hello from New Jersey, USA to all jag lovers around the world.

I am having an issue with the heating/air conditioner system the just went from bad to worse on a 1986 xj6 vanden plas. I bought the car in 2013 from someone in southern California where it had been for 4 years. Prior to that it was in Idaho where it was fully restored with an LS1 and HLR60 transmission. I don't think that has anything to do with my problem but figured I'd throw that info in in case it factors in.

Anyway since I have owned the car, the heating system vacillates from hot to cold for no apparent reason (at least to me). I can tell when is going to switch as I hear air sounds from under the dash and what sounds like the vent doors moving. It does the same thing in the summer when the air conditioning is running. When it works the heat and cooling temps feel fine. Any ideas on that particular issue.

Now for the wierd part. Last night I was driving it and out of no where I start smelling what appears to be cooling fluid and steam/mist begins coming out of the vent openings. I checked the radiator reservoir and it was really low so I added fluid and it seemed to stop the steam/misting issue but the dash controls stopped working. But heater continued to run hot air via floor vents but no where else. Air has never come out of these vents before.

I have no idea where to even begin. Any thoughts would be greatly appreciated

Have great day

Kevin

 

My bad transmission is 4L60E

 

"Probably" a faulty climate control amplifier, as that's the most common culprit when theses systems behave erratically.

But.....

There are other possibilities. Cabin temp sensor giving skewed signals. Air tube to the sensor not intact or leaking. Temp control rheostat faulty.

The factory service manual has some diagnostic trees and, if you can find one, the "Delanair Mark II training guide" is a really great resource for troubleshooting...or even understanding how the system works.




Sounds like the heater core is starting to leak. Big job to replace, sorry. Separate issue from the erratic operation...unless the leak is migrating onto some of the electricals

Cheers
DD

 

yes, start by getting a replacement Amplifier from Jaguar conversions, swaps, parts, service and advice - from John's Cars in Dallas. it is easy to disconnect the old one and connect a new one. As to the coolant smell and steam out the vents, check that there are no coolant leaks anywhere else in the engine bay. As a last resort you can add Stop Leak compound to the cooling system to try and close any pin holes in the evaporator.

 

Thank you all for the responses. I was afraid to start it today as I am concerned about electrical fire. I did check out all the hose connections and I see no leaks anywhere either in the engine compartment, garage floor or inside the cabin. Finally got the nerve to start it and drive for roughly the same distance as last night when the problem began and the dash controls are operational again and system is back to working erratically as it has since buying the car. Heat is good and and I hear the air releasing sound and what appears to be the vent doors changing position. Then air goes cold. Hear it again and air goes hot again. Luckily it's not that cold here today. Does that change anyone's opinion and/or recommendations or is this jags being jag nuisance issue.

I did take some of the panels off the center dash console to see if I could see behind the dash. Ha! There was so much stuff there I dared not go any further but I did not see any fried wires or connections.

Regard

Kevin

 

The amplifier is still a likely culprit. It commands the servo. The servo makes a whirring noises as it operates the linkages and also operates vacuum valves.

The amplifier takes information from the two temp sensors, the temp control , and the mode control. Using that it info it 'knows' what command to give the servo

With patience and a volt-ohm meter, and the manuals, you can test a lot of the parts individually. More often than not it comes down to replacing the amp

Cheers
DD

 

Cool thank you doug

 

Delanair Mark II Automatic Climate Control

Here is a link to a package of Delanair info. It includes the decision trees that I think Doug may be talking about. Hope it helps.

 

Kevin, very little chance of fire unless there is a serious gasoline leak in the engine bay. What you hear is the system going from Heat mode to Cooling mode. Set the Mode switch to AUTO, and the Temp switch to 75 or higher for Heating. When in Heat mode, the top Center vent is closed, air comes out the side dash vents, the floor vents located on each front side of the center console, and thru the rear of the center console for heated or cold air to the rear passengers.

 

The anti freeze smell does sound like a leak in the heater core. Replacement can be quite difficult as it requires removal of the HVAC unit for removal and replacement of the core, which can be an opportunity to inspect, test, replace and rectify any issues that are unseen. Or, there is a way to remove and replace the core the the HVAC unit in place. This involves dutting the inlet outlet pipes to clear the other things in the way for pulling the core, and doing the same thing to the new core with some lenths of 3/4" hose to replace what was cut off and a couple more hose clamps.
But I recommend removing the whole unit, it's such a great way to become one with the exquisite engineering of our fine vehicles

 

Or, just join the heater pipes at the vacuum valve. No more coolant
to the heater core. No more fluids and vapors in the cabin.


But, no nice warm air, either....


Long shot: Low refrigerant, odd cool, no cool cycles.


Possible: Vacum leaks. Two spigots under the battery. Hose from intake. One way valve. resevoir under brake booster.


And, those behind the dash !!


LS1 is a fine swap. My LT1 is not as advanced, but works really nice.


Carl

 

I've also had some problems wit my aircon