On my 1989 XJS Shooting Brake project:

I am assembling the interior presently and want to avoid taking it back apart and so I'd like to test the HVAC system.

But! I don't know when it last worked, if at all (car was not drivable when i bought it) AND the AC system is presently unpressurized.

So, can I test for valve operation, heater blend etc with the compressor not hooked up/pressurized? Should it be electrically connected but leave the belt off?

Where should I start inside the care? From what I've read this is a very complicated AC system and has multiple functions and since I've never experienced what it SHOULD be doing I'm wondering what I should be looking for-that make sense?

 

This is for delenair MKII and may provide some insight.

http://andthatsjazz.org/jaguar/s1002.html

 

I think the '89 should have the MKIII system. See this thread for the manual and testing procedures:

https://www.jaguarforums.com/forum/x...-manual-83961/

Cheers

 

Thanks for that link.

Good grief is this system complicated. It also appears that the repair for every fault is "Replace electronic control module."

Cute.

 

It's not that the system is any more complicated than on today's cars, its that there is no or limited self diagnosis capability. The XJS is a case study in why every manufacturer has gone way beyond OBD2 self diagnosis on new cars, to include every major system. Fault finding got to be so complex, customers were demanding features, and repair shops couldn't fix problems, forcing manufacturers to add diagnosis. The Delanair III system at least has a controller. The Delanair II system is a series of cam shafts, microswitches, and pneumatic valves that is an electromechanical nightmare.

 

In reality that's seldom needed.

The first step is checking the micro-connectors for corrosion and cleaning if needed. That alone can bring things back into proper operation....and is required anyway because none of the electric tests can be trusted if the connections are corroded. Clean the grounds as well, of course.

Cheers
DD

 

Yes

Of course, without refrigerated air you can't test how wll the system self-regulates cabin temp but you can check the fundamental operation



Sure, taht's Ok, ut I don't think it has to even be electrically connected


Some preliminaries:

Select max cooling on the temp dial. The heater valve should close. All air flow should be directed to the center dash vent. Fans should operate at high speed until the cabin cools, the fan speed drop and the air flow should be blended to away into the side vents and floor vents. The center vent should close

(This assumes the cabin is hot/warm. If the cabin temp is already below about 60ºF the system may not see any reason to go into cooling mode. Use a hair drier to heat up the cabin temp sensor a bit)

Select max heating. The heater valve should open, almost all airflow switches to footwell vents

Select defrost. Heater valves opens. System defaults to max heat and fan speed and almost all air goes to the windshield.

Select a medium temp. Heater valve should open, air goes to foot and side vents, system will blend heated and cooled air to regulate temp. But, of course, without the compressor running, it can't do that very well. The system is design so that all incoming air is refrigerated first (even when heating is called for) and then heated as needed.

Cheers
DD