tomcat59alan · Sep 6, 2013

Hi, Wonder if anybody can help. This has been posted on the Jaguar forum but what a waste of time. 1990 XJ40 electrical problem. Key in ignition to position 2 all dash lights on. Turn to start, nothing. Central locking ,wipers, indicators and gear shift interlock not working. With the ignition on the starter motor can be shorted to start the vehicle. If you disconnect the battery(brand new Bosch) and touch the leads together (capacitor discharge?) then reconnect, the car will start and everything will work. When you switch off its back to square one! Items changed include brake pedal switch, all relays, c/l control, ignition switch and the linear switch. Any ideas welcome

Chrisfrain2007 · Sep 6, 2013

I think you may need the jaguar equivalent of rave!

Dippypud · Sep 6, 2013

tomcat59alan said:
Hi, Wonder if anybody can help. This has been posted on the Jaguar forum but what a waste of time. 1990 XJ40 electrical problem. Key in ignition to position 2 all dash lights on. Turn to start, nothing. Central locking ,wipers, indicators and gear shift interlock not working. With the ignition on the starter motor can be shorted to start the vehicle. If you disconnect the battery(brand new Bosch) and touch the leads together (capacitor discharge?) then reconnect, the car will start and everything will work. When you switch off its back to square one! Items changed include brake pedal switch, all relays, c/l control, ignition switch and the linear switch. Any ideas welcome

Does the alarm work as normal ?

tomcat59alan · Sep 7, 2013

Dippypud said:
Does the alarm work as normal ?

Yes it appears to be. the fault is still there with the alarm switched off. I had downloaded the equivalent of Rave and it is very unhelpful.

Datatek · Sep 7, 2013

tomcat59alan said:
Hi, Wonder if anybody can help. This has been posted on the Jaguar forum but what a waste of time. 1990 XJ40 electrical problem. Key in ignition to position 2 all dash lights on. Turn to start, nothing. Central locking ,wipers, indicators and gear shift interlock not working. With the ignition on the starter motor can be shorted to start the vehicle. If you disconnect the battery(brand new Bosch) and touch the leads together (capacitor discharge?) then reconnect, the car will start and everything will work. When you switch off its back to square one! Items changed include brake pedal switch, all relays, c/l control, ignition switch and the linear switch. Any ideas welcome

So the problem only occurs on switch off? Something is preventing the Jag equivalent of the BECM, assuming it has one, from shutting down correctly, really the only way forward is diagnostics to check for example the the FOB receiver is not playing up. That, the alarm system or the BCU itself would be my best guess.

tomcat59alan · Sep 7, 2013

Thank you for your responses, I posted this problem for a friend and he will be watching for any suggestions as I am away today for a month. Think your idea is logical Datatec and that is the way to proceed. thanks again

naki · Sep 9, 2013

is the alarm OE jag or aftermarket?
aftermarket alarms are know to cause all kinds of problems. i had an intermittent immobilizer fault on the 1993 daimler xj40 (Cobra alarm).

you may also want to ask the question on XJ40 • Index page

its also worth checking the inertia switch is not triggered

also check or any damp/ water around the fuseboxes in the left and right footwells. xj40s have a habit of leaking water into the footwells that can cause all kinds of electrical issues

tomcat59alan

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Chrisfrain2007

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Dippypud

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tomcat59alan

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Datatek

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tomcat59alan

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naki

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