XJS Air-Con......Myths and mysteries

[dhdove]

Dear All

Reading the posts on this thread again it occurs to me that whist some of us have a vague idea about the air-con systems on our cars, all of us (with some honourable exceptions) seem to be scrabbling about in the dark on the subject.

As you know I have previously asked Nigel Thorley to run a dedicated air-con seminar and he said that there wasn't the demand............

Whilst I know how an air-con system works in principle, it is the control and feedback systems on the Jag that perplex me.

If you also think this is the case please contact him yourselves......over the whole range of models I am sure there would be enough owners who would like to see this mysterious system explained? At least to the point where we could do basic fault diagnosis - I know that for repair you need specialist equipment, but if we had an idea of exactly how the system works and therefore what the fault is, at least we could move ahead............

What do you think?

Best Wishes

DH Dove

[poprivet]

Steve's website is always a good place to start CLICK HERE
Re a seminar, I think NT is correct, the control systems have changed a lot over the years, to be of use a seminar would have to be very model specific which would reduce numbers considerably I would imagine. Even the xjs system ranged from the mechanical Delanaire II to the last facelift model.
The workshop manuals also contain a lot of information, but without the equipment to go with it is difficult to put to use. It is difficult to separate the control side from the refrigerant side of the AC system as a whole as they all work together and need to be tested together.

If you look up the price of a recovery unit, gauge manifolds, electronic scales, charging cylinder, leak tester, UV lamp, recovery canisters, oil and dye injectors, hoses, canister heater, electronic thermometer, bulk refrigerant, OFN cylinder hire, OFN gauge with hose, vacuum pump, training and certification you may decide it isn't a DIY hobby. Oh yes and thats before the cost of the parts actually needed for the repair

BTW, has anyone yet come up with a simple solution to switch off the A/C compressor at the same time as closing the re-circulation dampers for cool days to save some fuel?
Pop

[Mark_B]

The SKJagtech delanair mk3 info is nicely presented and the data easy to find. There might be some inherited errors that had originated from my delanair mk3 website. If so, my apologies.

A seminar I think is a good idea, but I'd say have the emphasis on diagnosis and dissassembly rather than how to repair. I think some basics can be easily taught. Need to remember these systems are a little beyond the repair capabilities of most. Electronics tends to be one of those things when more faults can be unwittingly added in the process of having a go.

I'll guess that diagnosing a defective solenoid or blower unit is about all that most will do. Then I believe there is a business opportunity for people repairing air blower units.

Ideally there ought to be a complete climate system fitted onto a demonstration unit where all the parts can be spread out on a board and seen in action under different stimulous and simulated fault conditions. And/or someone clever could build a java-based working model of it that runs on a webpage, complete with the controls sensors etc.?


There is a switch you can add for switching off the a/c. I put my switch next to the lower air vent. A 2 pole switch (DPST). Disable the compresser and recirc flaps together with one click. Had to locate the 2 relavent wires coming out the ECU, one of them is the solenoid for recirc actuator, the other the feed to a relay that energises the a/c clutch, cut them, splice some 4 wires between here and the switch.

I'm not sure if what I did was same as the 'Gardner/Napoli Mod' mentioned in Kirby Palm's 'xj-s the book' (newsgroup postings collected over several years, nicely indexed)

[almcl]

With respect Pop, I disagree.

A lot of the Mk 2 Delanire can be diagnosed without any refrigerant being present. Just having a unit out of the car and hitching a bit of vacuum and electric to it would enable many of the functions and failures to be explained. The Mk 2 system was fitted to XJ and XJS models for more than ten years and the Mk 3 for almost nine. Covering these two systems in a day, at least as regard to linkage and flap operation shouldn't be too taxing and would cover a lot of the Series XJ models and nearly all the XJSs.

All three manuals that I have (SII XJ, SIII XJ and XJS) include a diagnostic routine that requires no specialist kit, just a sequence of selections. From these an astonishing amount can be deduced about the health or otherwise of the system but they are seriously hard to follow possibly because the technical authors didn't understand how to present 'either or' decision tables. Working through this system and explaining the logic would be quite a good basis for a seminar, I think.

Having said which, Dave Marks's demo of rebuilding the IRS attracted less than 60 members so Nigel may well have a point. On the other hand it may just be that Dave M doesn't fancy setting up an air con system to run 'on the bench'.