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Re: Foglight check control - Help (more) (archive)

[ Follow Ups ] [ 5-series (E39) Message Board ] [ Msg. Board FAQ ]

Posted by Jim Cash on January 27, 2000 at 17:04:33:

In Reply to: Foglight check control - Help (more) posted by NW on January 27, 2000 at 14:28:26:

: My foglight check control (CHECK FRONT FOGLAMPS) comes
: on for no reason. Then, I turn on my foglights and
: the check control goes off????????

: This has been going on for two weeks, every time I
: start or turnoff the car - "CHECK FRONT FOGLAMPS"
: always come on - the only way to shut it off is
: to turn on my foglights (which of course work).

: My dealership has no idea.

: Anyone with a solutio? Thanks in advance.


I would suspect a high resistance in the bulb connector, or a partially deteriorated filament in one of the bulbs.

The system checks the bulb circuits when they are on, and whenthey are off. It does it whenthey are off by sending a very brief 12v pulse to the bulbs every 2 seconds - does not light the lights because the pulse is just a few milliseconds in duration. This is enough to check that the circuit is within resistance specifications.

So if there is any corrosion in the connection,or the bulb is now beyond tolerances the system will report a fault.
Applying fulkl voltage by turning on the lights will often overcome any small extra resistance in the circuit and your lights will seem to operate properly - but there will be a reduction in current and light due to the extra resistance in the circuit.


Try cleaning the connections at the bulb, or replacing the bulbs.

You have to pull off the small grill beside the foglight to get access. Remove small plastic rivits under top lip of grill piece and then just pull it out - pull hard.

Cheers
Jim Cash


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