Tail light issues?

[Username]

I have a 85 c20, recently put a new bed on it (had a utility bed swapped it out for a oem pick up bed).

My problems are as follows.. All rear lights work, however when I hit the brakes all rear running lights go dim instead of lighting up, now if I take the bulb out and turn it around to the brake side of the socket it stays lit but when I have it in the correct place they only go dim. Grounded in 3 different places on clean metal. Hazards work as they should!!!! That's what's got me confused?

And then my other problem. Before I starting messing with these lights the turn signals in the front worked, now they don't, right or left doesn't matter I get nothing front or back. Hazards work fine front and back. Flasher is brand new.

I should add I have no reverse lights either, this is the least of my worries and I really don't care if I figure this one out just thought I'd throw it in
Any help would be appreciated I just wanna get this truck on the road!!!!!

 

[hatzie]

There are TWO flashers... one for Turn and one for Hazard.

In 1985 the Turn Flasher power (Circuit 36) and Backup lamp power (Circuit 75) are from the same 10A ATC fuse. I guarantee it's blown. It's marked (TURN B/U) in the fuse panel.

The Hazards and Stop lamps are on a different 15A ATC fuse. Marked (STOP HAZ)

Since the Hazards work the problem could be in the backup lamp circuit.
Pretty easy to find out. Replace the fuse and try the turnsignals. If they don't fry the fuse start the truck, leave the RH or LH turns on and put her in reverse. If the turn signals stop, because the backup lamps fried the fuse, fix the backup lamp wiring.

The dim brake lamps could be a simple as a dodgy brake pedal switch or as nasty as bad STOP contacts in the column turnsignal switch.

The 1985 GM CK Light Truck wiring diagrams are in my signature.

 

[Username]

So, I replaced the back up turn fuse-it was blown, threw it in reverse lights came on, put the lh signal on worked for about 2 clicks then blew it right away.

 

[hatzie]

The Hazards work just fine, the running lamps light up fine, and the backup lamps are OK. The wiring to the back is probably OK.

If you replace the fuse again and just run the RH turns does it blow out?
If no... does the fuse blow with just the LH turns?

No blow means you have a problem in the backup lamps in the tail harness.

If the fuse blows on the turns along with the dim Stop lamps. It's sounding like you have a turn-signal switch problem but I'm not positive.

You can plug a turn-signal switch into the harmonica plug on the column to test without stripping the column down and installing it.

BTW when you get this fixed...
if you want a little better light in the back replace the 1157 turn bulbs with Sylvania 3496 bulbs and the 1156 backup bulbs with Sylvania 3497 bulbs. The Sylvania 3496 & 3497 bulbs are made in Taiwan so they meet spec... Most of the others are Chi-Com garbage.