RedDirtRodz

Here is a weird one. 66 coupe, new factory-type wiring harness. The front parking lights work like they are supposed to. When the headlights or brakes are on, the rear lights indicate the correct side, when the headlights or brakes are off, however, both sides blink regardless of which direction the signal lever is in.

Because the fronts work and the rears are not, I am lost. Ideas? The column and column wiring is original. The rest of the vehicle's harness is all new.

6D2148

That sounds a little weird, and opposite of what I would expect in relation to other lights on or off, But I would still say you are missing a ground at the rear lights, or bad bulb filaments Chip

RedDirtRodz

All new ground wires with new taillight housings. Grounded to the frame through the new harness. I will check it to make sure I have a good ground at each housing.

6D2148

Any difference in brightness, when they are working properly or improperly, or between one side or the other?

RedDirtRodz

Same.

watson

This may not help, but I had a similar problem on my 67. The problem was in the turn signal switch. A lot of the rear lighting circuits go through that switch and they can easily contact each other if there is any wear in the switch. If you have a new turn signal switch, it may be one of the repo's that have this problem all of the time. The repo switches seem to be too flexible and that allows wires to contact each other.

Doc

plaidside

This is how I would check the lights.
Take a jumper lead and connect one end to a constant power source, check the other end with a working test light to be sure.
Disconnect the connector at the signal switch and power up the Dk. Green and then the Yellow at the car harness side.
If both lights come on each time then it is in the wiring harness.
To check the switch, power up the purple wire at the signal switch connector, then turn on the left or right signal and using a test light check the Dk. Green and Yellow terminals.
If they both are lit then the signal switch is defective.
Joe

RedDirtRodz

That is excellent information, thank you! The car is headed to the SEMA show this afternoon, so I will have to address this when we get back.

champs65

My 65 does this from time to time. A quick L-R-L-R of the switch and its fine. I should replace the switch though. (It IS a repop about 6 years old)