Headlight switch

[troylasar]

Looking for a little help here with my ‘77 gmc k15. I’ve had this truck for the better part of two years now and most of that time has been without headlights. When I first got the truck I had no headlights, no dash lights, no taillights. All exterior cab lights worked as well as all side markers. I swapped out the old headlight switch for a new one as well as the connector for the wires, and wired it up exactly the same as the old one. I was expecting this to only fix the no headlights issue, but rather it fixed my taillights and dash lights. Thought maybe it’s the floor dimmer so I switched that out with a new one too, no change. Getting a bit dark out sooner so I thought what the hell I’ll try to get these headlights working one way or another. Today I swapped out the new headlight switch back to the old headlight switch, leaving the new connector for the wires in. That fixed my headlight issue sorta, pic for reference, and also brought back the dash lights issue but not the taillight issue. Anyone ever experienced something like that with theirs?

 

[rancher1913]

check the ground above the e brake, there should be multiple wires hooked together that ground evrything in the dash. no ground=no power flow

 

[PrairieDrifter]

Put the new switch back in then check all your grounds. Cleaning them is a good idea anyways.

All those lights look very dim even with truck off low ish battery

Check battery cables

2 grounds on core support for each headlight

1 from firewall to back of the pass head

1 from core support to pass frame rail

1 ground above ebrake

Should be 1 ground behind taillight, possibly 1 behind each. That changed in late 70's

 

[Dejure]

Interestingly, my headlight switch was physically broken, but still working when I replaced it. With the new one on, issues popped up. Got my meter out and checked the floor dimmer a couple times. Went to ohms and, low and behold, the new switch was garbage (Chinesium?). Installed another and all was well again.

I miss the days when we could respect manufacturers (they didn't expect the consumer to be the quality control department).

This doesn't look like that (e.g., dim lights), but a good reminder that we cannot trust every new part, even if we had to take a second mortgage on the neighbor's house.

 

[troylasar]

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This picture was the one time I had headlights with the new switch in a couple of months ago leaving work with my dash lights, taillights, turn signals and side markers all lit up along with the headlights. Could it be a bad ground from the headlights if the passenger side is dim but all the rest of the lights were bright?

 

[Ricko1966]

The headlights ground to the radiator support. 1st just wiggle the head light socket connectors. It is not the ground by the e brake,the taillights ground to the bed. I do not suspect that ground either,because they worked with the old switch. Just for fun check the fuses make sure you didn't pop one while you were messing around. If it was a fuse you shouldn't have taillights or dash lights but on a 50 year old truck who knows what people have done. Id get out my multi meter and check continuity on the switch you just removed. Headlights and taillights are 2 separate circuits on those switches they get 2 separate powers 1 for headlights 1 for tail/dash there are separate out puts for tail and headlight test your switch if it tests bad replace it. If it tests good check the harness you wired in a check for 2 powers to the switch.

 

[troylasar]

I cleaned the connectors on the back of the passenger side headlight, one of them was loose and had backed out a little and I pushed it back in and secured it with some electrical tape on the back. Headlights are nice and bright with the old headlight switch in, still no headlights with the new switch at all. I’m thinking I got a broken headlight switch so I’ll order another hopefully better quality. Strangely enough with the old headlight switch, I cleaned all the contacts and got the dash lights to come on, but no taillights. I thought dash lights cut themselves off if the taillights weren’t operating to let the driver know but maybe I’m ill informed on that. I’ll order a new headlight switch and swap it out and post an update after.

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[Ricko1966]

I cleaned the connectors on the back of the passenger side headlight, one of them was loose and had backed out a little and I pushed it back in and secured it with some electrical tape on the back. Headlights are nice and bright with the old headlight switch in, still no headlights with the new switch at all. I’m thinking I got a broken headlight switch so I’ll order another hopefully better quality. Strangely enough with the old headlight switch, I cleaned all the contacts and got the dash lights to come on, but no taillights. I thought dash lights cut themselves off if the taillights weren’t operating to let the driver know but maybe I’m ill informed on that. I’ll order a new headlight switch and swap it out and post an update after.

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The dash lights are on a dimmer the tail lights are not so separate circuits so you don't dim your tail lights. Now that brings something interesting,any chance you flipped the 2 when you wired in your pigtail and have rotated the dimmer?. I'd get a pinout of the switch. Verify I had everything connected to the right pin and check continuity on the pins of the old switch,then you can verify or rule out the switch as the problem.

 

[troylasar]

The dash lights are on a dimmer the tail lights are not so separate circuits so you don't dim your tail lights. Now that brings something interesting,any chance you flipped the 2 when you wired in your pigtail and have rotated the dimmer?. I'd get a pinout of the switch. Verify I had everything connected to the right pin and check continuity on the pins of the old switch,then you can verify or rule out the switch as the problem.

I wired the connector exactly how the old one was, which originally solved my taillights and dash lights not working. Using the old switch with the new connector: headlights work, dash lights work, taillights don’t work. Using the new switch with new connector: headlights don’t work, dash lights and taillights work. That’s why I don’t think it’s my wiring to the connector but instead a faulty switch maybe with something broken on the inside that gives power to the headlights. Tested all the wires with the new switch in and hi/low is the only wire getting no power

 

[Dejure]

Tried to find the drawing (wire diagram) I made, but no luck. I did a search to add the info and found this, which may help you (the video) with regard to the switch condition:

https://www.go-parts.com/garage/ps-1975-1986-chevrolet-c10-headlight-switch?srsltid=AU7gw4Xzc_ZiZJ9v_hRwNn7kvyEvKMN4s1WwDo1tQq2TtAOjIMnjWEYU

Note the video doesn't show what you'd read with the jumper removed, so doesn't show what circuits are fed from the fused input (5) then by the jumper to 1.

 

[troylasar]

Well, finally got everything working light-wise about a week ago. Left for work this morning and no dash lights or tail lights again. I’m thinking a wire burnt up on the connector because I could smell it while driving with my lights on but ignored it for a few days.

I’ll dive into the connector in the morning when I can see what I’m doing. Pics from the night I got them working again.

Anyone have an idea on how to prevent the wires from burning up again?

 

[awar]

Check your license plate light, I had the one on my pickup short out and blow the tail light fuse.

 

[Turbo4whl]

Are they LED headlights?

 

[troylasar]

Check your license plate light, I had the one on my pickup short out and blow the tail light fuse.

I actually don’t have license plate lights because the socket for it was rusted out and the previous owner tied the wires off

 

[troylasar]

Are they LED headlights?

Halogens for the headlights I think maybe my side marker lights are LED