The Stovebolt Site Forums The Shop Area The Electrical Bay Directionals Yes, Tail & Brake No

My truck is a 65 the directionals work but no brake or tail lights. Also when brake is applied tails keep blinking. I have found some good tips on the GMC site but just wondering is there any common thing that would cause this problem before I start testing everything. This being Mothers day weekend I will not get in much garage time in so just planning on the best way to attack this. I guess it could be a combination of the headlight and directional switch.
One more thing the 3 wire connector I have read about on the fire wall going to the rear lights I am correct in thinking that I can just pull this connector apart at the firewall(inside)
Ed

Ed sounds like a ground problem to me. A little strange to lose the brake lights and have turn signals my guess is the brake light circuit is being back fed and working as the ground for the turn signals. Run a temprery jumper wire from the ground at the fuse block to the rear where the taillight assembles ground to test this theory.

Oh this may help to standard color code for lighting is Green-right turn, Yellow-left turn, Brown-tail and White-ground.

ok that sounds like a place to start
Thanks

i am having the same trouble with my 60 mga. drove home from work and a coworker pulled up beside and told me. go figure. ron

Turn signals should flash the brake light filament of your bulb. Tail lights should not blink. The only way they will is if the bulbs are not grounded and the circuit is going through the tail light filament to find a place to ground.

make sure you have a good ground wire from the box to the frame, I had the same problem on a '79 Chev truck, 8 bolts holding a metal box to a metal frame and not one was a good ground. :confused:

I ran a jumper from the negative battery terminal to the base of the light where the bulb connects still nothing. I did check the bulb it is good. Next I need to find my meter and start checking for power to the other wires. I have a connector at the back with 3 wires I will start there and work my way foward.

if the turn sig works, there's nothing wrong at the light - if the turn sig keeps workin when you hit the brake, that's how it's supposed to be - the brake wire goes from the power supply, to the brake light actuator switch, to the turn switch, and when one signal is on, that interrupts that brake signal, supplying it's own power [brake applied or not], and it uses the brake light wires from the column to the tail

I'd start at the front and see if there's power to the brake light actuator sw [mechanical that the pedal arm controls, or on the master cyl], if that power isn't getting to the turn sw, no brake lights - having a factory wire diagram is a real help - the fact that you also have no tail lights makes it seem you have a bad connector ahead of the turn signal

Bill

could not locate my meter so tried using test light best I can tell the switch is not getting power. Was not sure what to test so tried every combination and no glow from the test light. I have a 79 Gmc parts truck from another project and I think the switch is the same if so I will try swapping the switch.

Did some checking today looks like it is the headlight switch I finally found a red wire on the headlight switch which is the incomming power I then jumped the red to the brown (tail light/brakelight) and had power and the brakelights were working. So I will replace the headlight switch and hopfully solve my problem.
Thanks for all the helpful tips