Electrical problems due to defective bulb

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Problems were press brake pedal and radio display goes off, but radio display does not go off with headlight on. All marker lights, including front turn signals and cab marker lights would light up when brake pedal depressed. Rt turn signal works with headlight off, but not with headlight on. It
would also flash all maker lights as well.
Lt turn signal worked normally and would not flash marker lights. I started out by disconnecting the right side wiring and everything worked normally on the left. I then reconnected only
the rt. side marker lights and left rt. tail light disconnected. Everything worked
normally. I then thought I had a short
in the tail lamp assembly. I connected the rt. tail light again and problems returned. I then pulled out the bulb, tried it out and everything normal. I pulled the bulb from the left side and put it on the right. Everything normal. I put the bulb from the right side on the left and problems transferred to left. I replaced bulb and everything works normally. Never heard of a bulb causing that kind of problem before. Funny thing is the defective bulb flashes
like it is good and tail light would turn on like it is good. Anyone ever heard of a defective bulb causing that kind of problems?

Would be a great bulb to sell to a dishonest mechanic in install in customer's cars. They could make thousands. Just kidding, already smashed it and into the trash.

 

[Archive]

Seems like bulb lost its ground using parking light wire to ground off of.
Maybe the connections in bulb were a little back words and when when brake ligh was activated sent juice down the parking light wire. Should be easy enough to check out by applying juice to brake light side of bulb with test light see if juice is coming from other connector or metal casing, you will have to supply ground also.

 

[Archive]

I've ran into the same problems more than once. Sometimes what happens is the turnsignal/brakelight element breaks and then fuses with the taillight element inside the bulb. Then the ground for the turnsignal or brake is provided by the taillight wiring instead of the ground. Yow can get some strange symptoms from the feedback. I bought a car that had the same problem, and someone ran a new wire all the way back to the taillights thinking the problem was the wiring. Turned out to be a bad bulb and a quick fix. I always tell someone who develops a strange problem like that to always check the bulbs first.

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'98 4x4 12V QCab Auto (ready to BOMB)