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Old 07-28-2003, 09:30 PM
tecqboy tecqboy is offline
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Join Date: Mar 2003
Location: Milwaukee Wisconsin
Posts: 1,149
I've just come across this posting and I find it extremely interesting from an electronic standpoint. I've read the posts all the way back. I don't have a diagram of the vehicle and I can't help you find the mystery diode. But two things I've learned from experience. Power diodes fail 99 times out of 100 by shorting and this almost always happens when they are asked to pass too much current ( like when something they are in series with shorts. ) A diode will almost always fail before a fuse blows. (Fuses take time to heat up and melt and are very slow; in electronic times.) Relays can have a partial failure. If a DP (double pole ) relay is say closed ( energized ) in position A and a short occurs, the NO contacts may be vaporized and open permanantly, but when de-energized the other circuit NC contact may still be OK. NO and NC relay circuits are wired into very complex logic circuits that make decesions like "if the door is open and the key is OFF, connect power to seat controller, but if the door is closed, the key must be ON to connect power to the seat controller. So if you have the wiring diagram you might be able to figure out the relay logic. If a relay is multi poled, all contacts must be checked. That means you need to have a way to energize them while testing; like a 12 volt battery or power supply. One more thing. If a relay is closed and the short occurs, it can permanently fuse the contacts closed. I've actually seen relays "heal" over time. The movement of the contacts will rub off burnt or oxidized material and restore operation.

OK, so this doesn't help solve your particular problem, but I hope it provides a bit of insight.

And the moral of the story is. Disconnect the battery before working on anything electrical in a car. This is especially true today when so many parts of the vehicle are actually being controlled by sensitive electrical devices.
Electronic engineer with 35 years experience keeping EVERYTHING electronic running down at the TV station.
Resistance is Futile.

Last edited by tecqboy; 07-28-2003 at 09:36 PM.
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