Quirky electrical fault, earth problem maybe?

A fault has developed on my '88 900i.

It first manifested the other night when I arrived home and switched off the ignition, except the engine did not stop and the lights remained on, until I took my foot off the brake then it stopped.

On investigation I find, with the ignition off, when I depress the brake the parking brake and brake warning lights dimly illuminate before a relay clicks, then these warning lights brighten and the headlamps illuminate and possibly the fuel pump spins up.

I found a mention on a forum relating to a similar fault where earthing faults were implicated but of course I can't find the link again :-)

Anyone else had similar problems?

Cheers all

Sam

Reply to
Sam
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Sam, Although I have not personally experienced the running engine symptoms, I did have lights coming on all over the dash one time, flashing in time to my right turn signal. I turned out that the connector to the rear tail lamps had a corroded ground connection. I ended up soldering an extra wire from the ground of the tail light assy to a spliced wire going to ground in the trunk. The ground on your '88 is further complicated by the "daisy chain ground" in the rear electrics. You should look at installing a wire from the (maybe both) tail light assy's to ground. I am pretty sure the tail light ground problem shows up on a forum search.

Good Luck

dave

Reply to
dave

There have beenseveral posts about "engine run on "caused by the headlight switch. Something breaks or shorts inside it keeping power to the engine when the key is "off".

Reply to
Spindle

Interesting, I have a spare switch ut away somewhere. I'll swap it over and see if that helps.

Thanks

sam

Reply to
Sam

All previous suggestions are sound & I've struck them all! While you're at it, pop both rear light assys, remove all the bulbs and clean any crap out of the sockets with a bit of fine emery paper, then reassemble and spray all the rear terminals with contact cleaner and allow to dry. May help temporarily or longer. Cheers

Reply to
hippo

Perhaps all the engine harness has lost all its insulation and are shorting wires together... earths sound good too..

my first bet would be cleaning up the bunch of earths where the battery neg mounts with all the headlight earths RHF of the engine bay, below the coolant drain.. lazy mechanics dont clean that area after draining the coolant, and thous leads and connections corrode very very quickly..

The other ideas from others are probly a good try too.

Mike

Reply to
Saab Master Tech

Hope not far too much hassle :-)

Yep checked there and on taking the bolt off to clean up, one connector and a bundle of cables decided to part company so I had to fit new ring terminals. Got everything bright and shiny and reconnected but the problems have remained :-(

On the bright side though the engine is running so much smoother it's like a different car :-) I would recommend this as a first look place on a car with poor low end running.

thanks

Sam

Reply to
Sam

Well swapped the switches and no change in the phenomena. Though I have now twigged that the engine running on doesn't happen with the headlights off so my feelings are more and more to a short/bad earth situation on the rear lights. At least now I have a headlight switch which doesn't rotate in it's socket :-)

Cheers

Sam

Reply to
Sam

Appears to have been a fault with the ignition switch. Sprayed copious amounts of contact cleaner into it, wiggled the key and bingo no more problems. At least it meant I sorted a couple of other problems :-)

Thanks all

Sam

Reply to
Sam

Have you changed any bulbs in the back lights recently?, If you put a single pole bulb in a twin pole bulb holder, eg stop and tail, then the single pole bulb shorts accross the two terminals thus allowing the current to back feed from one circuit to another and it is very possible it would create the problem you describe, Regards Tom

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Reply to
saabtech

There may be some sort of issues with the rear light clusters but not serious.

The cause of the problem turns out to have been a fault in the ignition switch. I fixed it by spraying it with contact cleaner. Probably due to years and years of food crumbs and dust.

cheers

Sam

Reply to
Sam

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