92 XJS Air Conditioning Questions

[PK1973]

Please bear with me as I am new to the XJS and I am translating from my mechanic. The problem I am having is as follows:

The heater core was replaced recently after initial purchase. On replacement the air conditioner was only blowing from the demisting vents at the top of the dash. Vent control having no effect on air direction. Upon testing my mechanic found good vacuum presure, but flaps werent opening all the way to deflect air. Motors were swapped demister for center, this resulted in air coming from center but not demister working that way until turned off. When restarting air was not coming from either outlets and no vacuum. The solenoid is only producing 5-7 volts. We are both reading over Kirby's documents as well as Jaguar repair manuals, however need additional guidance.

Questions we have are:
What should voltage be at solenoid be carrying? 12volts?
By swaping motors with one working partially is the original center motor bad/since its not working in the position of the demister?
Could the problem be with one of the computer control units which seem to be everywhere on the XJS? If so which?
Any other suggestions as to how/what to trouble shoot?

Thanks in advance

 

[jessebogan]

Having the defrost flaps open is the default position. No vacuum usually produces this. All solonoids should be 12 volts activated, 0 volts off. The drive for the servos is from the AC ECU, the piano looking thing on the right side of the climate control box. To make diagnosing the climate control a whole lot easier, I reccommend that you get the factory wiring diagrams(S57 for XJS) and also get the same thing for the equivalent year XJ40. They can be found on Ebay if you look. The XJ40 diagrams have all of the input and output voltages for everything in the system. The systems are nearly identical, so having both diagrams in front of you helps. You can check everything for proper voltage, and the diagnosis is a lot faster. That being said, the center vents on XJSs are notorious for failing. They can be accessed only by removing the dash.

 

[PK1973]

Thanks alot for the info, and will look for the diagrams. I have had the car only for a couple months and I am still learning where the bugs and are at. The first two months were to make it mechanically sound, now I'm on the creature comforts.

 

[Michael J.]

Under the radio is a slide lever that determines the amount of air going to the top vents as well as to the foot wells. What position is the slide lever in?

 

[Don_Neff]

> Under the radio is a slide lever that determines the
> amount of air going to the top vents as well as to the
> foot wells.

In my 1991 XJ-S that lever controls only the temperature of the air from the center vent. It does not vary the volume of air from any vent.

 

[PK1973]

Michael,

Had to grab the pastic and order parts, still waiting on delivery. Solenoid, motor and AC ECU (ouch)

 

[Michael J.]

Is your system R-34 or R-12 or R-12 converted to R-34?

 

[PK1973]

It is the Delnaire III system with no mods that I am aware of.

 

[PK1973]

The vehicle was an ebayer and within my intial price range. The moment it came off of the truck, I went for gas and car wash. After going through the wash the windows started to fog up. Turn on the defroster and whooooooooooosh.....
Water into the cabin, fried radio and since then been working on what I can or out sourcing to dealer and local garage.