Brake Lights- Weird Issue

[Matador]

I have a 1987 Chevrolet R10 with some brake light issues.

The right rear one works fine. Both tail lights at night work. Both rear turn signals work. The left tail light, though, doesn't work.

I thought this was going to be a broken wire, but the schematic I looked at shows that both the turn and stop functions run off the same wire.

Any thoughts?

[69chevytrucker]

change the bulb double element bulb one element must be toast

[Matador]

They're double element bulbs!?

Well, I feel like an idiot now. On Tuesday, I'll have to pick up new bulbs, then.

Any brand recommendations? Apparantly my last ones were garbage!

[chengny]

the schematic I looked at shows that both the turn and stop functions run off the same wire.

They do - and they also share the same filament (32 W) within that dual element bulb.

The lead to the LH directional/brake from the cab is yellow (all the way to the lamp).

The directional/brake light lead for the RH side comes down from the cab as a dark green. However for some reason GM decided to change it to yellow at the rear lighting harness plug. So the brake/directional leads running all the way down from the cab to the harness plug are yellow (LH) and dark green (RH). But if you look at the wiring diagrams (or the actual wires at the back of the lamp assembly) you'll see that they are yellow where they terminate on both sides.

Whether those yellow/dark green wires/filaments are receiving steady current (via the brake light switch ) or an intermittent power supply (via the directional flasher) is a function of the turn signal switch position.

If the brakes are applied, both sides get a steady power supply from the brake light switch. However, if the turn signal stalk is moved to operate the directionals while the brakes are on, it moves the switch inside the steering column. The contacts fed from the brake switch are opened and the contacts that are fed from the directional flasher are closed. As you can imagine there are two sets of contacts for each side. This (the turn signal switch) is where your problem probably lies.

The other filament (2 W) in that dual bulb is for the parking light. The parking lights on both sides are fed from the cab by the brown wire. The brown lead comes directly from the H/L switch and is hot whenever the switch is pulled out to either position. That wire is also spliced into the feeds for the rear markers and license plate lamps.

The hot wire for the back up lights on both sides is light green.

[Matador]

I think I sort of have an idea. I put new bulbs in the back to be safe, but that didn't do it, so...

I thought about it and figured out that my turn signals are doing it. See, my multifunction lever doesn't control the turn signal rotating contact disk-shaped assembly in the column. I use a finger to manually turn the disk.

If the disk isn't in the right spot exactly, one of the brake lights doesn't get current.

My question: What should I do with the turn signals? Replace the entire multifunction lever assembly or go with a metal On-Off-On toggle switch somewhere?

The multifunction lever will control everything else, but won't hook up to the turn signal control assembly.

Thoughts?

[MountainGoat1966]

If it was my truck, I would fix it right using good quality OEM type parts.
Less hassles with wiring and no modifications necessary.
A new switch isn't that expensive and preserves the look of the truck.

[Matador]

What would be needed? The switch does everything else just fine, but doesn't connect to the turn signal mechanism. Is there just a couple of screws missing, or does the lever need to be replaced? Does the turn signal mechanism itself need replacement?

The last owner did a really poor job on replacing the ignition lock cylinder. Any thoughts on what I'll need?

[Just call me Sean]

Use a factory switch, anything else wouldn't be smart. That switch/circuit is pretty complicated.

[Matador]

This part is fine:


The problem is with the multifunction lever connecting to it. The lever sits limp on the column. You can pull it up or down, but it falls back down. The wiper and headlight bright controls work fine. I'm assuming a couple of screws must be missing, or there must be a broken part of the lever or the turn signal switch?

Thoughts???

[hatzie]

The AC Delco switches are available from Rockauto and Amazon. They are pretty reasonable on price. Oddly enough the stalk itself is the pricy piece.

The turn, brake, hazard, and dimmer are in one switch assembly, wipers are in another switch assembly, and K34 Cruise Control switching, if you have it, is in the stalk with a wire through the column.

While you are in there you may want to evaluate the wiper switch. It's just as nasty to replace one as it is to do both...

Don't forget to tie a string, as a pullling aid, to the old switch harness before you pull it out of the column and be sure to get the wires on the correct side of the plastic guard.

[Matador]

I stole this image from another thread. His has a tilt column. My column has no tilt, no wiper delay, and no cruise control.

This is what I am turning by finger. How does the lever connect to the turn signal assembly? I'm assuming that the screw on the left is the one that connects to the lever, and the two on the right are for retention only?