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Old 02-20-2022, 07:58 PM   #1
71gmcC15
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Headlights don't work and it's not the dimmer swich.

Like the title said. Dimmer swich is new and the wires are in good shape. The problem. I got home and and turned the hi beams on because I wanted to see what they looked like at night. Headlights when dark. Spamed the dimmer swich got them to come back on. Then hit to go back to lows the whent out and they never came back on. All other lights work. This happed before with the old dimmer To. I could aways get them back but now I can't. I checked fuses to see thare is no fuse. I have power going in and out of the dimmer but no power to the headlights. Got any suggestions.
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94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
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Old 02-20-2022, 08:38 PM   #2
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Re: Headlights don't work and it's not the dimmer swich.

Check the terminals. A lot of dirt gets down there.
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Old 02-20-2022, 09:08 PM   #3
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Re: Headlights don't work and it's not the dimmer swich.

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Originally Posted by truckster View Post
Check the terminals. A lot of dirt gets down there.
It's all clean.when I put the new dimmer in I put new connections on it to.
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94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-20-2022, 09:14 PM   #4
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Re: Headlights don't work and it's not the dimmer swich.

https://www.youtube.com/watch?v=Tlzdq2nVCcE

Good video on how the Head Light switch works. Maybe it will help.
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Old 02-20-2022, 09:44 PM   #5
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Re: Headlights don't work and it's not the dimmer swich.

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Originally Posted by Accelo View Post
https://www.youtube.com/watch?v=Tlzdq2nVCcE

Good video on how the Head Light switch works. Maybe it will help.
I got power at the dimmer so the headlight swich is working. Great that makes it harder. Must be a under hood issue. I'll take the bolk head connector off the fire wall see if I got Power coming out. If I do then it's a problem between the headlights and the bulk head connector. ( broken wire? )
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-20-2022, 10:40 PM   #6
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Re: Headlights don't work and it's not the dimmer swich.

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Originally Posted by 71gmcC15 View Post
I got power at the dimmer so the headlight swich is working. Great that makes it harder. Must be a under hood issue. I'll take the bolk head connector off the fire wall see if I got Power coming out. If I do then it's a problem between the headlights and the bulk head connector. ( broken wire? )
If that checks out OK it may be a bad ground to the core support. Run a wire from the battery ground post to a cleaned bolt on the core support.

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Old 02-21-2022, 12:40 PM   #7
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Re: Headlights don't work and it's not the dimmer swich.

It may be a good idea to check the headlight bulbs to make sure they didn't burn out, just carefully connect the lugs directly to power using some test wires with alligator clips.
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Old 02-21-2022, 12:43 PM   #8
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Re: Headlights don't work and it's not the dimmer swich.

Now-a-days just because the switch is new doesn't mean it's not bad or it didn't break internally first time out. Power comes in at the top of the switch and low or high beam come out the sides at the bottom.
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Old 02-21-2022, 01:49 PM   #9
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Re: Headlights don't work and it's not the dimmer swich.

$5 says its the switch
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Old 02-21-2022, 02:18 PM   #10
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Re: Headlights don't work and it's not the dimmer swich.

Quote:
Originally Posted by LockDoc View Post
If that checks out OK it may be a bad ground to the core support. Run a wire from the battery ground post to a cleaned bolt on the core support.

LockDoc
I don't have power at the light socket. And if the ground was bad my side markers would aslo not work. Thare aftermarket led 3 wire. I grounded them to the same spot as the headlights. When it gets nice out again hopefully this weekend I'll check the bulk head connector
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-21-2022, 02:22 PM   #11
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Re: Headlights don't work and it's not the dimmer swich.

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Originally Posted by jimijam00 View Post
$5 says its the switch
I hope your right. I'm going to jump the wired together by passing the swich to see if that fixes it.
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-21-2022, 02:44 PM   #12
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Re: Headlights don't work and it's not the dimmer swich.

electric issues are a process of elimination and easy when you think methodically. Don't just buy a bunch of parts and throw it at the problem.
get a probe light tester and check for power at the socket. If you have power at the socket then fix ground issue.
if no power at socket then test backwards towards the power source, Ex. in and out of the switch.
if no power at switch test back to fuses and power supply.
eventually it will lead you to the problem.
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Old 02-21-2022, 07:10 PM   #13
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Re: Headlights don't work and it's not the dimmer swich.

Quote:
Originally Posted by rockyrivermark View Post
electric issues are a process of elimination and easy when you think methodically. Don't just buy a bunch of parts and throw it at the problem.
get a probe light tester and check for power at the socket. If you have power at the socket then fix ground issue.
if no power at socket then test backwards towards the power source, Ex. in and out of the switch.
if no power at switch test back to fuses and power supply.
eventually it will lead you to the problem.
Dont have power at the socket. Have power at the dimmer. So headlight swich is good. Bulbs are not burned out. Thare is no fuse. If it was bad ground my sidemarkes would not work either. Thare tide into the same ground as headlights. High beam indicater still works ti so the dimmer is switching the power like its sappose to. The problem is between the light socket and dimmer swich. I haven't bought any parts yet. To poor for that. When it get nicer out above 20F I'll dig deeper. But now it's not worth freezing.
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-21-2022, 08:40 PM   #14
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Re: Headlights don't work and it's not the dimmer swich.

Update. Made a quick bypass harness for the dimmer switch. It is not the dimmer. I can send power to the low beam and I here a relay click no lights. Try the hi relay click indicater lights up no hi beam. Is the relay bad? Or what? Agin no power at the socket not a ground issue. It's a power issue.
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-21-2022, 09:00 PM   #15
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Re: Headlights don't work and it's not the dimmer swich.

Are you saying you hear a relay clicking? There is no relay in the stock system.
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Old 02-21-2022, 09:16 PM   #16
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Re: Headlights don't work and it's not the dimmer swich.

Bypass the old wire and run new wire from the dimmer
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Old 02-21-2022, 09:31 PM   #17
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Re: Headlights don't work and it's not the dimmer swich.

Quote:
Originally Posted by dmjlambert View Post
Are you saying you hear a relay clicking? There is no relay in the stock system.
That's what it sounds like. Under the dash. ( maby a circuit breaker)I do have a HD headlight harness with relays on the core sapport. but I've experienced this before I installed it. Always got them to come back on. But now they dont Gess I could try hooking the lights up factory and see what happens.
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-21-2022, 11:02 PM   #18
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Re: Headlights don't work and it's not the dimmer swich.

The headlight switch has a circuit breaker built into into it. I read the whole thread once but am not looking back, have you replaced the headlight switch?
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Old 02-21-2022, 11:46 PM   #19
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Re: Headlights don't work and it's not the dimmer swich.

If you are running a relay do you have power into and out of the relay? What is your power source into the relay?
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Old 02-21-2022, 11:49 PM   #20
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Re: Headlights don't work and it's not the dimmer swich.

If you can hear a relay click and since you have eliminated some other areas, take a good look at your relay(s). Some relays have built-in blade fuses that might be bad.
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Old 02-22-2022, 12:19 AM   #21
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Re: Headlights don't work and it's not the dimmer swich.

Quote:
Originally Posted by Mike C View Post
The headlight switch has a circuit breaker built into into it. I read the whole thread once but am not looking back, have you replaced the headlight switch?
It would appear that there is something downstream out of order. You are correct about the headlight switch having a breaker on it. I'm interested on seeing where this goes, in terms of the final repair.
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Old 02-22-2022, 07:15 AM   #22
71gmcC15
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Re: Headlights don't work and it's not the dimmer swich.

Quote:
Originally Posted by Mike C View Post
The headlight switch has a circuit breaker built into into it. I read the whole thread once but am not looking back, have you replaced the headlight switch?
I have not replaced the headlight switch
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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Old 02-22-2022, 07:20 AM   #23
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Re: Headlights don't work and it's not the dimmer swich.

Quote:
Originally Posted by BigBird05 View Post
If you are running a relay do you have power into and out of the relay? What is your power source into the relay?
I will have to check. To see if power is coming out of the relays. I know power is going in. Fuses is good and is hooked straight to battery. Then the relay gets. triggered by the factory wiring to swich between hi and low beam. But the thing is it's done this before I ever installed the HD harness. But was always able to get them back. The only reason I installed the harness is because the dimmer would get so hot and melt the terminals. Maby it damaged the headlight swich to and now it Finlay gave out?. As in it sends power to the dimmer but the circuit braker tripes and doent send power out to to headlights idk. I'll check the relays when I get a chance though.
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)

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Old 02-22-2022, 07:48 AM   #24
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Re: Headlights don't work and it's not the dimmer swich.

If the dimmer gets that hot, you have to big of a power draw. Can you draw a schematic of how you have your relays wired?
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Old 02-22-2022, 11:50 AM   #25
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Re: Headlights don't work and it's not the dimmer swich.

Quote:
Originally Posted by BigBird05 View Post
If the dimmer gets that hot, you have to big of a power draw. Can you draw a schematic of how you have your relays wired?
It doent get hot anymore with the relay kit. It's basically the same thing as the lmc harness but actually works.
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( second times the charm) 71 gmc c15 307 sbc 373 rear gears positrac sm 465 trans. ( not listed on spid but is original )
94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless
07 gmc sierra classic rcsb 4.3 lt 5 speed w/t
04 chevy Silverado 1500 ext cab 5.3 4l60e.
81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green)
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