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Re: Where the filament monitor relay located Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Mon, 23 Sep 2002 12:19:15
In Reply to: Where the filament monitor relay located, Tom, Mon, 23 Sep 2002 06:44:40 Members do not see ads below this line. - Help Keep This Site Online - Signup |
As KeithR says, it's in the relay box behind the glove box. It requires removal of the glove box, not hard, but not a happy thing. A probably not required.
The filament monitor works by comparing the current through the brake light bulbs on the left and right sides. If the current doesn't match, it assumes a bulb is out. Yes, you could trick it by having all the bulbs burned out.
Unfortunately, in the earlier years, the filament monitor used a method with balancing coils and mechanical relays. Not good as it was too sensitive. In later years Saab went to a solid state unit that worked better. But even the solid state unit can be tricked.
If the bulbs have bad connections, bad grounds especially, then the current through one side will differ than through the other, triggering the monitor. So remove all the brake light bulbs and clean the bases and contacts with a little fine sandpaper. From the bulb circuit board there is a black wire that runs to a ground point on the chassis. Unbolt the ground point and clean the contacts, again with fine sandpaper or some Scotchbrite. Bolt everything back down nice. If the problem persists, try Keith's idea of using bulbs from the same manufacturer. There is a (good) chance that there are manufacturer-to-manufacturer differences in the bulbs, resulting in different current draws. If you use the same vendor left-to-right, it will minimize differences.
Good luck!
posted by 192.249.4...
, Mon, 23 Sep 2002 12:19:15 <-- Viewing This Message, Mon, 23 Sep 2002 17:13:45
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