harrisonm said

Thanks for all the replies. I did have a bit of a grounding issue with the left front parking light. That's fixed now, and the culprit was fresh paint (good call). After hours of testing and looking at the wiring diagram, I finally figured out why my brake and turn signal lights were not working. I ultimately determined that the wires on the back of the cheap Dorman turn signal canceling cam were not making contact with the electrodes on the top of the turn signal switch. The back side of the cancelling cam has two hard wires about one inch long that make connection with four electrodes on the top side of the turn signal switch. One of those hard wires is hot when the ignition switch is “On” and the other one is hot when the brake pedal is depressed. The four electrodes on the top of the turn signal switch are sort-of in a square. Using a jump wire, I determined that the upper right hand (UR) electrode sent power to right rear tail light, the lower left hand (LL) electrode sent power to right front parking light, the upper left hand (UL) electrode sent power to left front parking light and the lower right (LR) hand electrode sent power to left rear tail light. So when the turn signal lever (that moves the cancelling cam and the hard wires on the back) is flipped up for a right turn, the wire that is hot when the ignition is on will contact the UR and LL electrodes thereby activating and flashing the front and rear right hand turn signals. Conversely, when the turn signal lever is flipped down for a left turn, the wire that is hot when the ignition is on will contact the UL and LR electrodes thereby activating and flashing the front and rear left hand turn signals. When the turn signal switch is in the neutral position, the other hard wire on the back side of the canceling cam (the one that is hot when the brake pedal is depressed) is making contact with the UR and LR turn signal switch electrode. So when the brake pedal is depressed, power flows to both rear tail lights. I bent the tips of the wires on the back side of the canceling cam up a bit so they would contact the turn signal switch electrodes, and everything worked fine, but I think I’ll still look for a better canceling cam.

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