This Electrical Control Unit is the suspect of some of my headaches.

It looks VERY expensive to replace even with a rebuilt. So ... any advice for troubleshooting the ECU to make sure its the problem?

 

Nathan:
I guess I'd get a replacement from a salvage yard. I'm sure Jagbits would be able to find one if you gave them a call - but any of the Jaguar-specific places are going to run into some bucks. Heck, try ebay.
I'm not saying that ECUs cannot fail, but in the short almost two years I've been learning about this car, I don't think I've ever heard of it happening. What is the problem you are hunting for which you think the ECU might be at fault? (Apologies if you have detailed that elsewhere and I didn't see it.)
Scott

 

I may have missed what the problems are as well.

However if you are needing a used replacement why not pop down to the Wanted Section and ask SPP a forum sponsor for a quote.


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I don't know enough about electronics to even attempt to be able to help with diagnosis.

 

The AC/Heat controls dont always respond. I found the ECU dangeling ... which could mean I just have some loose connections. I'm going to double check those and the blower motors (I only have heat defrost) and vacuum lines today as well.

 

Nathan:
There is an excellent chapter on aircon issues (particularly a nuisance on the 88s & 89s I understand) in the XJ40 book at the Jag-Lovers sight. You may already know about it, but here is a link. Beyond that, I have no personal experience with these issues except for praying against never having to worry about them on my car! Best of luck. I'm sure you'll get it all sorted out with time. Cheers, Scott
http://www.jag-lovers.org/ebooks/vie...j40&Vsection=9

 

Hoskins,

This is what could happen when an A/C ECU goes bad:

http://www.jag-lovers.org/include/iv...Cf6WmMgzuRQ%3D

Regarding the ECU, If you found it dangling, make sure all the connections are seated properly, as well as the ground. It attaches via two screws in the vicinity where it's located.

I think your problem is related to the micro switch associated with the A/C Control knob. Those do go and can easily and inexpensively be replaced . If the ECU did in fact give up the ghost, I got mine on Ebay. Make sure you get the correct one for your model.

 

Nathan:
Since I posted my ignorance above, I read two recent posts by Fritter and Jess who BOTH have experienced A/C ECU failures! Sorry if I misled: but I do think the suggestion regarding the A/C knob is a good one. Any luck? Scott