I'll admit I shouldn't have been messing with the relays, but I was
trying to figure out why my left brake lights won't work even
though I know the bulbs are good and there is no corrosion on the
harness. Incidently, if you can help me figure this out too I'd be
much obliged.

So I was pulling the relays looking for evidence of corrosion. An
error message showed up on the climate control and the car wouldn't
start. I disconnected the battery and reconnected - to no avail.
Then, I tried to recharge the battery (I'd been working for awhile
with the headlights on). The recharging unit kept declaring the
battery charged and the lights all over the car were pulsating. I
decided to disconnect the battery and then recharge it . . .
finally, I reconnected it and got the car to start.

But, when it started the backlight on the intrument cluser was out
and (strangely) so was the light on the cigar lighter. I've
checked all the fuses - nothing wrong there. I'm worried I either
have a bad relay or I've fried something somewhere.

Any suggestions? I love this car but I'm a student without much
money to really put into a bunch of electrical wild goose chases.

 

You are quite certain that you have checked all of the fuses under the heelboards in the back seat?

The backlight on the binnacle can go out if the PECUS loses it's programming, and with what has happened with the battery and relays, that is possible, but I would suggest that you take another harder look at all the fuses. Do you have a chart of where they all are and to what they pertain?

Peace!
Jack

 

Jack,

Thanks for the response. Yeah, all the fuses are good for sure. I've got a diagram under the hood which tells me what they all pertain to. I was thinking maybe the dimmer switch has gone bad, but that wouldn't explain the tail light or the cigar lighter light. Aparently there is a tail light modulator? Could that be the problem? I don't think the tail ight issue and the dash light issue are at all related, but there might be a relation between the dash light and the cigar lighter.

BTW, what's a PECUS? I did a search for it and found something about a photoelectric switch. It seemed to suggest it was an automatic switch depending on the light level (like street lights which come on when it gets dark). I'm not sure how it would apply to the car.

 

The PECUS is the Programmable Electronic Control Units System which is an advanced vehichle management system that replaced the previous Digital ECUs on Jags in 1994. It is not a photoelectric switch, it is part of the ignition system, it controls the EGR, Lambda's etc...

There is a lamp failure module in the trunk. I believe it is that aluminum box just the other side of the fuses in the trunk fuse box.

BTW, that diagram under the hood doesn't quite tell the whole story when it comes to what is connected to what.

Peace!
Jack

 

Thanks Jack. I'm worried it might be the PECUS, because the ignition continues to be iffy. Sometimes it will turn over but die immediately (unless I give the gas pedal a good pump) and sometimes it won't turn over at all unless I disconnect/reconnect the battery. Is there any way I can verify whether that unit is working on my own, or should I just take it to the shop?

Ben

 

Ben,

I think this would merit a trip to the shop. You might try disconnecting the battery again for a few minutes and then reconnecting it. If that does not work, take it to someone who has some experience with these vehicles.

How many miles does your car have BTW?

Peace!
Jack

 

Hey Jack,

Well, I went back through and tightened my battery terminals and checked the fuses again because I had heard that even a slightly loose terminal could interrupt ignition and because I also had heard from you and others that any other cause but a burnt fuse for the backlite on the dash being out is highly unusual. Basically, I found a burnt fuse (I really couldn't believe it when I found it because I swear I checked that very fuse multiple times) and replaced it. The lights are back on. Between that and the tightening of the terminals, everything appears to be back where it was originally. That means I'm still working with the left tail lamp, but I'm glad to only have that to worry about. Thanks a bunch for your advice. To answer your original question, I've got 82,500 miles on the car.

Ben