I'm having strange electrical trouble with my 92 XJS V12. It's been stored for 2 years and when I powered it up although it started first time a lot of the electrics were dead. And by a lot I mean most.

Cleaning all the grounds I could find got some things working, but with a weird delayed start.

Nothing happens for a few minutes (up to 5 mins) then the power to the blower comes on and with it the power to the windows, indicators, radio (but not the antenna) mirrors, ABS, and seats. I'm using the noise of the blower as my cue - it could be one of the other systems comes on and the blower is down the line.

What would cause this delay? I can't find anything like this online.

Any help would be appreciated. Thanks in advance.

 

In case you haven't, check the battery voltage. Really weird stuff happens with an old battery.

 

Agreed on needing a 100% battery.

My gut feeling is loose/dirty/corroded connections are at play here. Good that you cleaned grounds. Now go and clean the "+" voltage supplies, starting at the battery and then the two "+" junction/distribution posts on the firewall. See if anything improves. If not, move to cleaning fusebox and relay contacts.

Cheers
DD

 

In my car (pre facelift) there are some relays in the boot, just by the RHS hinge corner where (on my car) the ECU is, one of these is the main load relay that powers everything up when the ignition is switched on. If you car is similar in this respect, it might be worth cleaning all the contacts and earths in this area up, as well as the other things already mentioned.

Greg

 

Basically cleaned every contact I can see - checked every fuse. Ran a voltmeter on most points to check voltage as well. There was one very badly corroded ground next to the drivers seat CU by the inner sill. Obviously rain wets the carpet when the driver's door is opened and it's in the perfect place to corrode. Cleaning that got most systems up initially with a small delayed start.

Now it's taking longer to come to life and it's clicking on and off. There is a loud relay click coming from the passenger well and the electrics go on and off.

I can't think of what's down there that controls this many systems. But, hey, it's a Jag.

Off now to test relays!!! Oh joy.

Thanks again. And if anyone has a brain wave I'm all ears.

 

A fully charged battery stops the clicking on and off (thanks for that one) - but there is still a delay (but shorter) to the electrics coming on. Even in this "power on" mode I'm now missing fuel and battery gauges, lights wipers and the aerial doesn't go up.

The full beam works but not the lights and the window washers, but not the headlight washers. Weird car.

I'll keep digging and cleaning contacts.

This is a 92 V12 XJS with only 27,000km (real) on the clock. Never had trouble with it up until this year. Oh well.

 

If you remove the shin level lower trim, you will see various electrics to clean up, maybe even hear and identify the one that is clicking? Also, there may, repeat may, be some electrics behind a removable panel under the footwell carpet at the more vertical part of the passenger footwell.

Greg

 

Ian. You should add car info to your signature to help identify which year and model.

 

Hopefully my signature is now changed - thanks for reminding me. Didn't see where to fill it in when I first joined.

Greg - Bonjour! Have removed every panel and cleaned every relay I can get to. Even started testing them yesterday... was slow and a real pain with wires, crocodile clips and volt meter.

Looks like I'm going to have to buy a relay tester.

Oh well. Onward and upward. Hopefully.

PS - Confused why a less than fully charged battery would cause a problem when the engine is running. Shouldn't the battery be less of an issue with the alternator providing power?

 

Apologies, I hadn't noticed the engine was actually running! What's the volts at the battery/alternator when its running?

 

Will check volts out of the alternator at the weekend. Up to my neck with work at the moment. What should it be? if you know off hand.

 

At battery.
Car idle - 12.7 volts
Car running - 14.2 volts

Anyone know if that is that good?

 

on spec.
Greg

 

How about the ignition switch contact?
It is linked to the key cylinder, inside the lower column cover.
Maybe worth checking the ohm at least.

 

Will check the Ignition switch today - Thanks for the tip.

And thanks for the confirmation the power is to spec Greg.

 

My relay tester arrived and all the relays I tested passed. However I found that some of the relay base connections in the front left engine compartment were broken. Replaced them - that was fun.

Now the electric mirrors work, all the gauges - including the battery and fuel that previously didn't. AND most importantly there is now no delay to systems coming on.

Windows, seats, etc now work when the ignition key is turned one click - ie no engine running.

So a lot of positives. But the horn stopped working - no idea why.

Now the wipers, headlight washers, antenna and lights (not flasher or full beam) are the only things not working.

There is power to the antenna (purple wire) and the relay seems fine. I think it is seized up. Will disassemble this weekend.

And I found that power lead comes from the wiper logic box to the lights. Going to check that. Think the wiper logic box may be at fault.

It seems that any electrical component can mess with a completely unrelated component in this car. I did nothing to stop the horn working and yet it is silent.

It must be love... or insanity.