Some rear lights not working

[Cook76]

Had everything working for inspection (fixed the back up lights and put in a new turn signal cam so they would cancel). Everything worked for a week. Get to the garage and both back up lights stopped working, left rear hazard quit and left rear brake light quit. All Signals and running lights still work.

Driving me nuts. Any ideas.

Thanks

 

[Broncobowsher]

If the right rear turn still works you know the bulb and wiring to the turn switch is still good.
If the left brake still works you know the brake switch to the turn signal switch is still good.
The hazard is actually hitting the brake switch for all effective purposes.
So that leaves you with a turn signal switch issue. Fairly normal problem. If you watch the reflection of the brake light against a wall and wiggle the turn signal switch you can often get the light to flicker if the switch isn't too shot yet. It comes down to you really just need a new turn signal switch.

reverse lights are an unrelated issue. Have you done any transmission or shifter work since the last time they worked?

 

[Cook76]

I'll fix the original post. It's the left rear that has the lights not working. sorry.

 

[Billsboat]

assuming the wire harness is original, I would start checking the different connections, ie with truck in back up mode, key on, start wiggling connections. Plug and un plug stuff. After forty years things do get corroded. If that does nothing start checking grounds. I've been dealing with the same thing on my 71. I'm thinking of doing a hole new harness

 

[Viperwolf1]

Had everything working for inspection (fixed the back up lights and put in a new turn signal cam so they would cancel). Everything worked for a week. Get to the garage and both back up lights stopped working, left rear hazard quit and left rear brake light quit. All Signals and running lights still work.

Driving me nuts. Any ideas.

Thanks

And that's why those replacement TS cams suck. The wire contacts are never quite right. That's where the problem is.

 

[Broncobowsher]

I'll fix the original post. It's the left rear that has the lights not working. sorry.

Same as I mentioned before, just replace the words left/right as the system is a mirror image.
Your tests already prove the wiring and bulbs are good except for what is inside the turn signal switch.

 

[Cook76]

Yup was the switch. Put a shim behind to keep it from floating around. Fixed.

On to the Back up lights. I tested both bulbs and they are good. With both bulbs out I have power at both sockets. I plug in one bulb and the power is gone.

 

[Viperwolf1]

Yup was the switch. Put a shim behind to keep it from floating around. Fixed.

On to the Back up lights. I tested both bulbs and they are good. With both bulbs out I have power at both sockets. I plug in one bulb and the power is gone.

You have a very poor connection somewhere. Get yourself a 12V test light and check all the connections. Fuse is good otherwise turn signals wouldn't work. First connection is at firewall where neutral safety switch plugs in. Maybe switch needs adjustment.