Brake Light Ckt Help?

[John Poling]

ItBites,

I am not familiar with the '59 truck column but will assume it is similar to other GM columns. You should have some kind of connector that connect the electricals of the column to the harness under your dash.

1) Bad or degraded grounds are the primary culprit in all electrical system failures. My first tests would be to verify whether all four tail lights really do share one ground or whether the two that are not working correctly share a ground of their own. I would bet that this is the case. To verify a good ground for your light, make as long of a jumper wire as needed to reach your battery negative (-) terminal from the ground wire on your tail lights, this will insure that you are at a true ground. Make absolutely certain that you are probing the ground and not one of the power wires. At this point check to see if your lights are working. If they do, repair your ground wiring in the rear. If they don't work, start probing your wiring from the tail light moving towards the front and find out where you lose your power at. Over time connectors have been known to corrode and lose their connection.

A couple of other ideas are as follows:

2) If you have 12v to your brake switch, depress your brake pedal to activate your switch and insure you are getting 12v out. Trace that wire up to where you can verify that it does or does not go through the turn signal switch on your column. Check to make sure your turn signal switch is functioning correctly.

3) Start at the fuse panel and trace out from there for the flasher circuit. This could still be tied together with the brake lights at the switch in your column.

In closing, electrical problems are the most difficult problems to diagnose because of all the loose, broken or corroded connections that are found in a typical automotive electrical system. I may be weird in stating this, I love to trouble shoot electrical gremlins as long as there is not electronic componants in the system. The only thing I like better is to put the system together from new, as to eliminate the probability of some of these electrical gremlins.

Please let us know if/when you need more input.

John.