F12 blows on '94 840 - help

[Marty]

F12, 15amp, blows when the outside temp gets below 38F. This happens irregardless of any cockpit settings or internal heat settings. I've experimented with this and have had all heat (fan, seats, etc) off, doesn't matter, it still blows. Sometimes it blows just after hearing the near freezing bell ring and other times it may take an hour after the bell before it blows, but none-the-less, it''ll blow.

F12 supplies power to the following: windshield washer heaters (I diconnected them with no effect), drivers memory mirror, mirror selector switch, passenger side memory/mirrow, automatic transmission range switch and the starter relay.

When F12 blows while driving the car, the only symptom is that the right alpha display of the two digit LED transmission gear display located at the bottom left of the instrument cluster, goes blank.

Once this happens, if you turn the car off, you can not start it again due to the fact that this fuse supplies power to the starter. Also, it will not allow you to change gears. You can of course select reverse or forward and they work fine, but shifting into D2,3 or 4 produces no results.

My thoughts lead to trying to find out what turns on automatically at that outside temp. Any ideas ?

Marty

[artherd]

I'd say you have a short in the washer heater somewhere after the thermostat, but before the mheater itself. (as you've disconnected them.)

Time to start checking with a voltmeter.


Best!
Ben.