The Stovebolt Site Forums The Shop Area The Electrical Bay Headlights Only Work on High Beam

Get to work. There are 24 hours in a day. People in China are starving. Brady is getting a divorce. Winter is coming. No time for you to watch I Love Lucy reruns.

Ya, I didn't get finished working today till late. I'll give the previous wiring guy credit for his wire wrapping skills. I only got part of the under hood wiring unwrapped today.

Still has the original cloth wrapped wires under the tape.

Winter? What's that? We haven't had one in Atlanta for quite a while.

That there is what you call your "Natural" color wire, with tracers. The Smithsonian may want that......so put some of it away in your underwear drawer.

Well now, based on your pics, I need to retract my recommendation to replace the wiring harness. Those wires are remarkably preserved. You may just need to replace any of them that have been molested.You can acquire lengths of those cloth wires of the correct color tracers from the folks who sell cloth wiring harnesses. Sorry, I don't know the name of the outfit who sells them. I'm sure that Denney Graham would help you with that if you send him a PM.

Yes, they don't seem too brittle, either. However, since I've already replaced the headlight wiring with modern plastic insulated wire, I don't think it will make much difference what I use from this point on. It's already a hodge podge.

I'll wrap the whole thing in a vinyl wire loom when I'm finished. Just to refresh everyone's memory, here it is last week when I drove it for work.

Original style wiring won't really dress it up much.

Don't leave it parked so close to that dumpster. Some helpful soul may get the wrong idea and help you load it.

Got that right.

Razor blades or a box cutter go a long way to opening up a loom quickly.

That truck looks exactly the way I like them to look. Perfect. Nothing better than a truck with all guts renewed with it's original patina skin and skeleton. See what I did there? That was a Halloween reference.

I'll be able to work on the truck tomorrow.

In case you aren't around Bartamos, what test should I perform next once I've isolated the center dimmer switch wire on the headlight switch itself?

You want to check the actual headlight switch terminal that the dimmer wire goes to. To see if that terminal goes hot when knob pulled out. If it does go hot every time, the problem is that wire. if it does not, It's the switch. That terminal will be hard to get to. So leave the wire on until you drop switch with all wires still on it, then test that terminal and report. I will be around and checking on what you say.

If switch is "bad" you can probably fix it. It's gratifying to fix. Getting it apart without damage is tricky but once inside it's just a matter of cleaning and light sanding the sliding contacts. There are springs in there to maintain contact between sliding and stationary contacts.....OR...

You can buy a new one from China.

Don't disconnect any wires from switch unless you label each wire and make a note and a drawing and take pics. We don't want to lose any possible cause of this loss of power to dimmer and never know how it was wired and in case of new switch, it will be easy to install.
I know it seems we are going slow and doing dumb stuff, be it is necessary or we will chase our tail.

Your in good hands with Bartamos, but I’ve been down that road before and I believe can add some insight. If you do buy a new switch, there are two types available. One is more of a generic switch that replaces everything including the knob, which doesn’t match the existing knobs, but is half the price. The second is a repop that matches the original switch and uses the shaft and knob from your original switch. I bought the later at classic parts and it worked perfectly. [LINK]

Additionally, I labeled my switch so I didn’t screw up the wiring.

Yes, I'm very methodical in everything I do. I've been drawing pictures and labeling things during disassembly since I was a kid. I still take pictures just in case.

Thanks for the photograph.

Are the three terminals on the end for accessories like heater, radio, etc? I assume those terminals are live regardless of headlight switch position?

Yes those end terminals are hot. Called "always hot". As opposed to "switched hot". You can use those for a voltage source, but not for heater or radio or any other components that could be left on and run the battery down. Those two would be run off the ignition switch.

Be careful, there are diagrams and pics of headlight switches on the internet that are incorrect. Member Deve has an incorrect one all over the place. His ignition switch diagram has erroneous info also. This is all on his "technical" website. He does have a lot of good helpful info.

NEVER use a wiring diagram that someone has redrawn on their sketch software and added colors and their own symbols. All electrical info here and elsewhere should be verified from GM documents. Feel free to question any info. We all make mistakes.

Phil's headlight switch wiring is correct.

Here's the switch.

I can pretty easily lay on the floor and reach everything so when I get the wire traced, I'll run the jumper wire and see what happens.

How is the switch removed? I couldn't feel a nut holding it in.

Hopefully I won't have to remove it.

Who said run a jumper wire? Where are you getting these ideas? This is very frustrating. Especially from a person who is "very careful". "Methodical".

To remove the switch:
There is a little button on the bottom of switch frame, hold it in and pull knob and shaft out of switch. Remove nut and retract switch out from backside of dash.

Maybe I'm using the wrong term.

After tracing and disconnecting the existing wire, I'll connect a temporary wire to the test light.

OK you take over from here. You will figure it out. Several ways to skin a cat.

The nut is a slotted collar on the outside of the dash. You have to remove the knob and shaft prior to removing the collar. There is a button on the switch (as Bartamos has pointed out) that needs to be pushed to release the shaft. You may have to turn the shaft one direction or the other to get it to release. Mine was not easy but eventually did give in.

Once the shaft was removed, a wide blade screwdriver was able to loosen it. There is probably a special spanner wrench that fits the nut.

I finally got the last of the black tape off and was able to trace the wire.

It goes up near the light switch but doesn't connect to the switch. It goes off toward the passenger side into another black tape wrapped bundle.

Did the factory wrap the cloth wires in tape? It doesn't seem like they would but whoever did it on this truck did a good job. It's murder getting that stuff off.

I'll see if I can figure out where the wire attached to the headlight terminal in Phil's photo goes.

The factory wiring diagram shows the wire going directly to the headlight switch. Doesn't show how the bundle is arranged or the path.....so I would stay with that wire until the end so we get educated. From what you describe it seems no one has been inside the bundles, but who knows for sure yet.

You can test that terminal on the headlight switch now that you see where it is. See if it has juice. Touch the terminal not the wire only.

Otto, please stay on track with bartamos. Resist the temptation to jump ahead or anticipate what he’s going to ask you to do next. Reread his post from last night @ 10:27pm. It sounds like the wire you have been following does not terminate at the switch. Keep peeling tape, you can always retape when this is all sorted out.

Here's some other information which might help.

The center wire from the dimmer switch is heavy gauge.

It comes up to a large bundle on the inner fender where it is connected to another wire and wrapped tightly in that old fashioned cloth style electrical tape. Doesn't seem "factory" to me.

The heavier gauge wire goes toward the front of the truck and the thinner wire goes up into the cab. This is the wire I traced. It is smaller gauge than the wire attached to the center terminal.

The wire coming off the headlight terminal on the switch is the heavier gauge wire.

Just FYI, all of the wires being discussed are the original cloth wrapped variety.

Two wires of unknown purpose elsewhere under the dash have marking tape flags on them -one yellow and one blue. Unless this was some system the factory used to help the installers, someone has been under the dash doing who knows what.

I'm wondering if the person who used the dime store connectors got the center wire mixed up with one of the side terminal wires?

Ice Pick test on the headlight terminal (according to diagram) shows it's hot when the knob is pulled out.

You could disconnect wire at headlight end and do a continuity test on that wire.

OK, the wire connected to the dimmer switch terminal on the headlight switch was connected to one of the side terminals of the dimmer switch.

Judging by the nearly permanent bends in the wires just as they attach to the dimmer switch looks like they've all been connected in those positions for a long time.

I think I'll try out for The Cirque de Soliel after getting in and out from under that dash so many times. I'm getting more flexible with each attempt.

Well at this point we are gathering info and maybe saving bundle rip out/untaping. So when both ends of "dimmer" wire are loose, do a continuity test on it.
If it shows open, I'm think of leaving it abandoned, and as you said, install a new direct wire. Maybe no need to keep undoing bundle. At least for this fix. See what you think. I just wonder why it seems to meander. But the factory does that sometimes. The best avenue is to follow it and say "Oh yeah" is goes there but in a round about way.

DID YOU SWITCH YOUR QUESTION? BIG EDIT? OR AM I HAVING A SIEZURE?

I already have Myasthenia Gravis

How it was wired explains why it did what it did. But does not explain why that wire didn't work when you connected it to the center terminal? I think you screwed up testing.
OOPs, didn't mean to say what I was thinking out loud

I never connected that one to the center dimmer terminal.

I just traced it a few minutes ago and discovered it was one of the wires connected to the side dimmer terminals.

The only new "corrected" wiring is from the headlights themselves to the new terminal block and from the terminal block to the dimmer switch.

I have not yet tested the wire on the headlight switch for continuity. It's been hanging free down by the dimmer switch since re-wiring the headlights to the dimmer since it was erroneously assumed to be one of the high beam or low beam wires.

Ok run a jumper from headlight switch to dimmer ASAP. Test. 5x

Then remove jumper and hook up the original wire AGAIN if it shows continuity. Test. 5x

Don't unhook the side terminal wires on the dimmer. Report both tests. ASAP.

I think we're both confusing each other.

The wire on the center dimmer terminal was never touched or changed. As we now know, it was never a hot wire.

When the bulbs to the dimmer wires were installed the two side terminals were removed. One of them we now know was the Hot wire from the light switch on the dash.

The "real" hot switch, which should have been connected to the center terminal, was now hanging in midair because it was thought to be one of the wires coming from the hi or lo beam of the headlights.

In any event, a jumper wire from the pull out switch to the center dimmer terminal works both hi and lo beam when the floor button is pushed.

So, should I connect the dangling wire that's already connected to the pull out switch?

Any thoughts on that weird splice of the cloth wires?

Must have been typing at the same time you were. I'll go test the jumper 5 more times.

Tested 5 times with jumper and headlights go on and off properly. So does hi-lo, lo-hi.

When you say "original wire", are you talking about the wire that's connected to the pull out headlight switch or the one that goes off to who-knows-where under the dash.

Maybe I was confused. I doubt it.

This may be a repeat of what you did already, or I said or didn't say, not going to search that sooooooo.......I will spell it out carefully so I don't screw up.

Here is the next step. If there is a wire attached on the correct terminal of the headlight switch and you know where the other end is, test that end for hot. If it goes hot, attach that other end to the center dimmer terminal and test.

If it does not go hot, or you don't know where the other end is.......take it off the headlight switch, wrap it up and install a new wire from headlight sw to dimmer. Ring tongue to ring tongue. Done.

Too much time spent talking about that center dimmer wire and it's history. What it is, What it was, what it was thought to be and if it's called original or not.

Gotcha

In other words, you dig my rap.

picking up what you're laying down