Another brake light question and a new one about my headlights

[ghostvbhc]

So, today I replaced the headlight bulbs and we thought that's the reason the headlights weren't working, but the high beams were working. Now again my high beams are working (and, they turn off after five minutes and turn back on after about a minute or two) and the regular headlights aren't working again. Also, my brake lights stopped working again, both of them this time with the lights on or off, but the blinkers work. Can anyone help me with these? I thought I figured out the brake light problem because they were both working just fine and now today they aren't working at all. Thanks to anybody that can help.

Oh and also has anybody hooked up a third brake light to a 69 c10? I bought one, but we don't know how to hook it up.
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[VetteVet]

You probably have a bad dimmer switch for the headlights. Look at the harness that connects to it and you'll see a blue wire a tan wire and a green wire. The blue wire is the power wire from the headlight switch. If you have a multimeter you can check for 12 volts on the blue wire with the headlight switch on. you can also jump between the blue wire and the green wire and the lights should come on.

If they do and they stay on then try jumping to the tan wire and the low beams should come on. If this works and the harness connector isn't corroded or otherwise damaged then the dimmer switch is bad. If the symptoms stay then check the firewall plug for corroded connections or the harness for bad or open wires. The circuit breaker in the headlight switch might be opening and closing but not likely cause the dims don't work at all.

There is an orange wire from the fuse panel to the stoplight switch that feeds a white wire that runs to the steering column to the turn signal switch.
It goes through the TS switch and connects with the dark green and yellow wires that are the turn signal wires for the left and right sides. When you select a left or right turn then the brake light for that side is opened and the turn signal works. /sometimes the turn signal switch won't make contact to the brake light contacts so the brake lights no longer work.
If you disconnect the half moon connector on the column and jump the white wire and the yellow and dark green wires . then step on the brake, the brake lights should come on. Again if you have a multimeter and check for 12 volts on the white wire with the pedal pushed it tells you the brake switch is OK and it points to the TS switch as the problem.

The easiest way to wire in a third brake light is to tie into the white wire off the brake switch or at the half moon connector and run a wire from there to the third brake light. Make sure the light is grounded to the frame or cab wherever you mount it. There are diodes an special harnesses you can order that will let you wire into the yellow or green wire too but they are more complicated.

[ghostvbhc]

Can you also tell me what this is?

[ghostvbhc]

Also, this is the third brake light we bought, so how would go about hooking the white wire from the half moon connector to it?

[ghostvbhc]

Quick update: My passenger side brake light started working this morning and the drivers side wasn't and if you remember the passenger side brake light was the one that wasn't working until I cleaned the ground wire and then both of them worked. And, after cleaning the ground wire and putting in a new non rusted screw on the drivers side for the brake light, both of them stopped working again. This is getting frustrating now.

[VetteVet]

Originally Posted by ghostvbhc

Can you also tell me what this is?

If you're talking about the box with the plug in the end, it is the external voltage regulator for the alternator. The black wires just above it are ground wires for the front lights, so take the bolt out and clean the connection down to bare metal. This may be your headlight problem and it will cause charging problems as well.

[ghostvbhc]

We're cleaning it as I'm typing this, so I'll keep you updated with it. Anything to help me with how to hook up the third brake light?

[VetteVet]

Originally Posted by ghostvbhc

Quick update: My passenger side brake light started working this morning and the drivers side wasn't and if you remember the passenger side brake light was the one that wasn't working until I cleaned the ground wire and then both of them worked. And, after cleaning the ground wire and putting in a new non rusted screw on the drivers side for the brake light, both of them stopped working again. This is getting frustrating now.

You definitely have a grounding problem on the rear lights. Is your truck a stepside or fleet? You may have a bad ground between the bed and the frame.
There are two connections for the rear lights on your truck. One is on the firewall just behind the distributor and the other is mid frame underneath. You might have bad connections on those, but if that were the case then you should see problems with the turn signals and tail lights.

[ghostvbhc]

My truck is a fleetside with a straight six in it. With my engine, there isn't a ground wire on the firewall behind the distributor.

[Tinkermc]

you have a problem that drives a lot of antique restorers absolutly baty.

[VetteVet]

Originally Posted by ghostvbhc

Also, this is the third brake light we bought, so how would go about hooking the white wire from the half moon connector to it?

The wire from the brake switch should be white but it appears that the one in the picture might be black with white stripe. On the other side is a solid white one and it looks like the harness that goes to the steering column. In either case the wire that you want to splice into will have 12 volts on it when you step on the brake. I would just move back from the harness about 3 inches and bare the wire and solder a new wire into it and then wrap it with a good insulating tape. it's already fused, so no need for that. You could use a crimp connector with shrink wrap and solder it too if you want a foolproof connection.



The wire that you connect into the white wire from the brake switch will go to the third brake light and if I were you I would use an orange/black stripe or at least an orange wire the same gauge as the third brake light, probably 18 or 20. Make sure you have enough wire to reach the third brake light.


Looking at the picture of your third brake light I see a black wire in the connector with the Orange/black wire. This is a separate ground wire that will have to be run to a very good ground in the cab that's also grounded to the frame. I would run it from the same area as the orange wire so it would be one taped harness. Maybe a brake pedal bracket screw is available. It also appears to have 2 bulbs in it which explains the second connector
(white). I don't know what to tell you about the black connector as far as how you are going to connect it to power and ground. If you don't have the other side of that connector then you will have to splice in the orange/black and the solid black wire or come up with a connector from the junk yard.

[ghostvbhc]

Okay, so wiring the third brake light doesn't sound too hard. It's the headlight and brake lights that are driving me crazy.

[ghostvbhc]

My headlights still aren't working after doing what you suggested and my brake lights aren't working anymore at all again. This is so damn frustrating it's ridiculous.

[yob2kanobe]

Headlight switch may be bad. This happened to me and it was the switch.

[ghostvbhc]

It might be, so ill have to check it. The only bad thing is we don't have a voltmeter.
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[ghostvbhc]

Can I also say that I've tried to trace the grounds from the tail lights and brake lights to the one that you're talking about on the frame in about the middle of it and I can't find that ground wire. It just hooks up to a connector at the frame right under the bed of the truck and then that runs all the way to the firewall. Can anybody help me find this ground wire?

[VetteVet]

Originally Posted by ghostvbhc

Can I also say that I've tried to trace the grounds from the tail lights and brake lights to the one that you're talking about on the frame in about the middle of it and I can't find that ground wire. It just hooks up to a connector at the frame right under the bed of the truck and then that runs all the way to the firewall. Can anybody help me find this ground wire?

I didn't say that was a ground wire, I said it was the connector for the tail light wires. There should be 4 or 5 wires in it and the other connector is behind the distributor. check them for corrosion.

You probably have a bad dimmer switch for the headlights. Look at the harness that connects to it and you'll see a blue wire a tan wire and a green wire. The blue wire is the power wire from the headlight switch. If you have a multimeter you can check for 12 volts on the blue wire with the headlight switch on. you can also jump between the blue wire and the green wire and the lights should come on.

If you run a hot wire to the blue wire it will bypass the headlight switch and you should get headlights with the dimmer switch connected. If you get nothing try jumping to the green or tan wire and you should get the bright or dim lights.

Here's the pic of the dimmer. The connector or the dimmer switch itself may be bad but if you jump the wires like I said you will bypass them.

[ghostvbhc]

Oh, okay I thought you were saying there's a ground wire in the middle of the frame from the tail lights, I'm sorry man. I'm a nineteen year old trying to figure most of this stuff out with my dad who used to own these trucks when he was my age. Ill check that wire for the tail lights today and try what you're saying with the headlights today and let you know how it goes.
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[ghostvbhc]

So, I changed the headlight switch, the dimmer switch, and the turn signal switch and now my brake lights work just fine, but I don't have any running lights in the back of my truck and my low beams still don't work. Any advice?

[ghostvbhc]

Still need some help on this please.

[72 K20]

You need to have a multimeter and a good test light and a wiring schematic can be a huge help when trying to trace electrical problems.

I believe there is a wiring diagram on this site
http://67-72chevytrucks.com/vboard/s...d.php?t=185856
It sounds like the bulkhead connector could be causing some problems,, take it apart on the engine compartment side and check for corrosion or burnt terminals.

Let us know what you find .

[marman101]

My 72 was driving me batty too. Tali lights and brake lights intermittently would go out...then they were back on. Then no tail lights or brake lights. I read all the stuff and changed out the brake switch and checked wiring. Still didn't work. Then, I decided to start back over again. I thought to myself " how about a bad fuse"? Well, it was a bad fuse. I felt rather stupid, but they do work.

Good luck.

[72 K20]

I just got done repairing an '83 K20 that had the no low beam problem. I could hear the circuit breaker popping when they were on low beam. It just about drove me nuts. I had changed out the light switch and the dimmer switch to no avail. I checked the wires running from the left headlight to the right headlight and found one wire out of the loom,,,, I pulled all the rest of the wires out of the loom to check them and didn't find anything wrong. I didn't think too much of it. After I did that I couldn't get it to goof up. I put the dash back together and was going to give up when I decided to put the wires back into the loom. When I was putting them back I had left the lights on and I saw a spark. Turns out there was a spot about 1/16 worn through the wire from being out of the loom and rubbing on the frame horn. I taped it up, put all wires back in the loom and then taped the loom where it crossed over the frame horn and all was golden.

It doesn't take much to mess up the lights,, this was on a 30 year old truck. Check all your wires for wear spots. When the lights mess up,, wiggle your wires around to see if you can make it change,, if it does, look in that area.

[mrein3]

Originally Posted by ghostvbhc

So, I changed the headlight switch, the dimmer switch, and the turn signal switch and now my brake lights work just fine, but I don't have any running lights in the back of my truck and my low beams still don't work. Any advice?

If your hi beams work and low beams don't, we know there is power down at that dimmer switch. Now either both low beam filiments in your new headlights are both dead (unlikely) or there is an issue with the low beam wire from there to the lights.

Take that connector off at the dimmer. Turn on the headlights. With a test light or a DMM figure out which of those three wires is hot. That is the wire from the headlight switch. We know it works because you said your high beams work.

Make a jumper. Connect one end of your jumper to that hot wire and the other end to either of the other two slots. One of the other two goes to your hi beams, the other to your lows.

Now. If hi works and low doesn't either the low wire is broke (unlikely) or your connector is furry, green, and needs to be cleaned or replaced.

You can remove the wire from the connector. There is a little tang you depress with a small flat blade screw driver from the connection end and pulling out the back. That is a "Packard Type 56" connector and can be purchased new at NAPA. I replaced all three of those connectors 18 years ago and haven't looked back.
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[ghostvbhc]

Thanks for all the advice guys, I'll be doing all of this when I get the time this weekend and I'll update when I'm done.