I had just finished fixing up a used Honda Odyssey for the dealership to sell, and it had been detailed and was going to be delivered to the customer in a couple hours, when it was given back to me because the left turn signal wouldn’t turn off. Regardless of switch position, the left turn signal would constantly blink when the ignition was on.
My first thought was to unplug the turn signal switch and swap in a good one if I could find one. As I started to take off the steering column covers, the turn signal suddenly turned off. I realized that it turned off when I adjusted the steering column outwards to have room to remove the trim. When I pushed it all the way back in, the turn signal turned on again. This meant that there must be a pinched wire somewhere.
Finding problems with wiring harnesses can easily take a long time, but fortunately I found the problem very quickly. The car had a factory accessory remote start installed in the past, which included wiring running to the headlight switch. When it had been installed, part of the harness ended up where it would get pinched by part of the steering column when it was adjusted. When pushed all the way in, the column would pinch the harness enough that it wore through the wire insulation on the signal wire for the left turn signal, grounding it and turning on the turn signal. I taped up the wires and tried to reposition the harness so it wouldn’t get pinched again, and put everything back together.
Mechanical Malarkey T-shirts, hats, and stickers are available to order!