Brake/Parking/Dash lights not working

[gringoloco]

I am double posting this from the electrical section to get some visibility. Anyone got any ideas? please help. Thanks -Chris

Originally Posted by me

So, toolin' along minding my own business, hit the left blinker and the stereo starts pulsing with the blinker. I figure I've got a short to ground somewhere and I won't use the blinker 'til I get to work a block away. Hit the brakes- same effect- no avoiding using the brakes- dammit!

Apparently this is the point when the fuse for that circuit blew. So, I turn on the hazards, hoping I don't get rear-ended by some moron while I have no brake lights. The radio was still pulsing with the hazards, soon blew that fuse as well...

Luckily got to work without an accident and quickly found the short in the obvious place- the brown wire in the rear taillight harness from some POs shabby hack job. Fixed her up with a butt splice and some heat-shrink and replaced the burnt out fuses(Tail Stop and Traffic)

Now I have a more complicated problem:

What does work:
-Blinkers
-Hazards
-Headlights

What does not work:
-Brake Lights
-Parking lights
-Instrument Cluster Lights

When testing the fuse panel, with the key on, all fuse circuits are hot on both sides except 'PNL. LTS.' This circuit is dead on both sides.

When testing the headlight switch, the red main feed is hot in all positions as well as the orange wire. The only effect the switch seems to have on any other wires is the lt. blue headlight wire which is hot with the switch all the way out.

I thought this may have been the problem, but swapped it out with a known good switch from my other truck with the same effects.

So, looking for some advice as to where to look next. I was thinking it could be the turn signal switch, as this will cause the brake light problems, but can't figure out why it would cause the parking/dash lights to go out.

The truck is no longer popping fuses. I assume this means I have an open somewhere.

Any suggestions? -Chris

[oldgold70c10]

On the headlight switch, power for the headlights themselves is fed from the 12 guage red wire, which is unfused right off the battery. Everything else is fed off the 16 guage orange wire which is protected by a 20 amp fuse. This fuse is in the fuse block and is fed via the "hot at all times" bus run straight from the battery.

Ans for the "PNL LTS" being dead:

The cluster lights actually have 2 fuses, one at the main feed (orange wires)before the light switch, and one after (green from the light switch to the fuse panel, then grey after the fuse panel to the cluster plug). The cluster lights, marker/parking lights, dome light, and brake lights are all on this one circuit. The brake lights are fed off of the dome light harness plug near the fuse panel, just trace the orange wire back from the brake light switch to the dome light plug. It junction at this plug with another orange wire that goes to the fuse panel where ith connects to the orange wire that feeds the headlight switch.

Somewhere, you've got an open in that orange wire. It could be where it connects to the fuse block. Does the dome light work? If it does, you should be able to get the brake lights to work, since they are fed by the dome light.

You may want to look at this color coded diagram, it will help considerably.
http://67-72chevytrucks.com/vboard/s...d.php?t=185665

Be sure to check for old and tired fuses, in fact, just replace all of them. You will save a lot of head scratching.

[gringoloco]

Awesome. This is exactly the info I was looking for. I spent a lot of time head scratching while looking at that diagram, and could not for the life of me figure out where these circuits all tied together.

You have given me a solid foundation for further troubleshooting.

Thanks -Chris