Headlight Switch Trouble

[n33k0]

I have been scratching my head trying to figure this one out for a while, even though I'm not the brightest crayon in the box when it comes to electrical stuff. The headlight switch in my truck doesn't work correctly, the only lights I can control with the knob are the headlights. Marker lights, dome light, even brake lights don't work when the switch is plugged in!

Somehow I figured that I could hard wire the connection in the plug to test the wiring. I removed the switch and found the hot "POWER" wire in the plug, then ran a short lead to each terminal to test the lights.

Run a wire from "HEADLIGHT" to "POWER" and the headlights turn on, "MARKER LIGHTS" to "POWER" and the marker lights turn on... When I have these three terminals wired to the "POWER", the lights are on and everything is great... but when I put the switch back on, only the headlights work.

If I have the switch on, I found that I could run a lead as shown in the pic below, then the switch would work perfectly... I can dim the cluster lights, I can turn on the dome light, the brake lights work too, but only if I run a wire as shown by the blue line.


What is happening here? there is obviously power reaching the switch... but I have tried three different switches and none of them work without the modification I have mentioned above.

Any help would be appreciated.

[1968aj]

im no electrician. does dimmer switch work properly? most electrical problems are bad ground.

[n33k0]

The dimmer work fine if I hard wire the plug as shown in the second pic. If the dimmer switch is plugged in without the (blue in my picture) wire, it will only turn the headlights on and off.

[Kennuck]

Sounds like your headlight switch is bad.

[n33k0]

Is there a good quality switch I should try? I've bought one switch from ClassicParts.com and another from NAPA, plus the one that was in the truck when I bought it, so far all three switches have had the same issue.

[LockDoc]

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I can't believe it's the switch if you have tried 3 of them but I guess it could be possible.

Here is a labeled picture of the switch posted by VetteVet. He labeled the "Brown" as '68 up. What year is your truck?

LockDoc

[n33k0]

Originally Posted by LockDoc

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I can't believe it's the switch if you have tried 3 of them but I guess it could be possible.

Here is a labeled picture of the switch posted by VetteVet. He labeled the "Brown" as '68 up. What year is your truck?

LockDoc

That's the reference I used when I decided to hard wire the terminals. My truck is a 1972 year. I went as far as taking apart the fuse box, and cleaned the contacts a bit. I didn't spend too much time under the dash though, since I figured "power is getting past the fuses, so the problem is not down here."

Looks like if I connect the "Done/courtesy" terminal directly to the "12v in", then the switch works correctly. But without the extra wire connecting the two, the switch only functions to turn the headlights on and off.

[VetteVet]

What you are missing is the orange wire power to the headlight switch. It appears that you have an orange wire to the switch plug which originates at the fuse panel.

notice the orange wire in the diagram that starts at the fuse panel in this pic.



This one shows the orange wire to the headlight switch. This is a full time hot wire so check it for power at the headlight plug, and at the tail stop fuse.
I can't seem to find it right now but I'll post it later if I find it.

[LockDoc]

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The "Orange" (Dome-Courtesy) terminal actually feeds the terminal labeled "Brown" through the switch when it is on. It is not fed from the "Bat" or "Power" terminal.

LockDoc

[jeffahart]

Originally Posted by n33k0

Is there a good quality switch I should try? I've bought one switch from ClassicParts.com and another from NAPA, plus the one that was in the truck when I bought it, so far all three switches have had the same issue.

I was told by AAW that there is only one company that manufactures the replacement switches. I have a low opinion of them, as I am on my third one. I am using my original switch, I cleaned it up and got the dimmer working which was the only problem with it to begin with.

[VetteVet]

......
Here's the diagram to the headlight switch.

In the first one it shows the orange wire in the middle of the fuse panel and how it's fed from the battery alternator junction. It branches off to feed the stop light switch , the dome light and the headlight switch brown wire for the markers and parking lights. If you don't have power there then those things won't work.

[n33k0]

Originally Posted by VetteVet

What you are missing is the orange wire power to the headlight switch. It appears that you have an orange wire to the switch plug which originates at the fuse panel.

notice the orange wire in the diagram that starts at the fuse panel in this pic.

Attachment 1450661

This one shows the orange wire to the headlight switch. This is a full time hot wire so check it for power at the headlight plug, and at the tail stop fuse.
I can't seem to find it right now but I'll post it later if I find it.

So I need to check that the orange wire is getting power at the fuse box? I remember seeing the orange connection when cleaning the back of the fuse box, but it didn't have a clip-on connection like the other wires, it was either soldered or crimped directly to the back of the fuse panel. Because of that I wasn't able to clean the contact surface, and didn't pay much attention to that connection.

If I understand correctly, the orange wire should have power all the time... it currently does not get any power unless I manually connect it to a 12v source with a spare piece of wire. Looking at the diagram, it looks like the orange wire gets its power through a circuit connected to the red wire on the back of the fuse box (black line connect red and orange wires)? Could it be that the circuit between the red and orange wires is broken (behind the fuse panel), and that's why everything works when I complete the circuit with the added wire at the headlight switch plug? Sorry if I got it all wrong, I don't have much experience reading wiring diagrams

[n33k0]

Originally Posted by jeffahart

I was told by AAW that there is only one company that manufactures the replacement switches. I have a low opinion of them, as I am on my third one. I am using my original switch, I cleaned it up and got the dimmer working which was the only problem with it to begin with.

Yeah, the switches that I have didn't stand up to regular use for very long before they physically broke. It seems that pushing the headlight plunger in (to turn everything off) eventually cracks the back of the plastic housing, leaving the interior electronics exposed. It definitely feels like a cheap part.

[jeffahart]

Originally Posted by LockDoc

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I can't believe it's the switch if you have tried 3 of them but I guess it could be possible.

Here is a labeled picture of the switch posted by VetteVet. He labeled the "Brown" as '68 up. What year is your truck?

LockDoc

This is a salient point, each "bad" switch I had suffered from a different affliction. So, if something works with one switch and not another that's a test. If same thing does not work on all switches it's inconclusive. Just hoping you can eliminate the switch as the culprit in your process of elimination. If you follow what Vet laid out you will be able to trace your issue.

[EARNHARDT#3]

If all 3 switches have done the exact same thing I wouldn't pay any more attention to the switch. There is likely something wron in your turn signal switch (a lot of things run through it) or your fuse panel/wiring harness.