Headlights Won't Come On

Tiny
DONNERMAN28
  • MEMBER
  • CHEVROLET SILVERADO
Chevy, 2007 1500P/U, 130,000, V8. The headlights won't come on when the switch is turned. The daytime running lights seem to work fine. I have checked the fuses and they seem to be o.K. I have changed out the light switch but it did not help. I checked the voltage at the headlight plug and found approx. 9VDC. The lights themselves look o.K. And had good continuity. Can you help me please? I love this site!
Saturday, August 18th, 2007 AT 10:19 PM

5 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Hello,

It looks like there is a low and high beam control relay in the system. If this relay does not work the low beams will not light up. Here is a guide to help you test the relay make sure the headlight switch is on.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Here is a guide to show you how to check for power at any given point.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Here is the headlight wiring diagram along withe the fuse panel location and identification.

Please let us know what you find.

Cheers
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Monday, July 27th, 2020 AT 5:31 PM
Tiny
DONNERMAN28
  • MEMBER
  • 3 POSTS
I will check the relay tonight when I get home. I checked the fuses for the lights in the relay box under the hood which checks o.K. All of the interior lights work along with the dimmer.

I checked the voltage at each position on the connector itself. The connector has a total of 11 terminals with a group of 4 and a group of 7. Two of the group of 4 have black wires which I believe to be neg (-). With the connector oriented with the four terminals on the right I found 12 volts on the far right terminal above the grounds and on position 3 (going from right to left) on the 4 terminals in the group of 7. I also found 12 volts in the middle postion in the group of 3 of 7.

I also checked the voltage for at the bulb connector once again and found 9.4 volts when the running lights were on but zero volts when the switch was turned for headlights? I am stumped!
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Monday, July 27th, 2020 AT 5:31 PM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Power comes out of the switch and goes through the Daytime Running Lamp Module (behind left side of dash) be sure 12 volts is getting through that, then it goes through the dimmer switch (hi-low beam) check for 12 volts through that as well, get back to me.
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Monday, July 27th, 2020 AT 5:31 PM
Tiny
DONNERMAN28
  • MEMBER
  • 3 POSTS
I poked around the steering column looking for the terminal for the headlight dimmer switch and while poking I decided to try the relay test you have here and sure enough the lights started working when I replaced the relay! YA.

Needless to say I was puzzled before be now enlightened by 2Carpros

I figure there was a wire grounding out? I thought the wiring harness on the back of the switch assembly was a plug and when trying to pull it out a wire came loose? I didn't really tug on it I think it was loose in the connector and when the wheel was tilted it either.

Thanks guys!
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Monday, July 27th, 2020 AT 5:31 PM
Tiny
WHIGHTOWER
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  • 0 POST
Thank you for the post it was the relay in my truck cost me $32.00 all good. I love this site
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Monday, July 27th, 2020 AT 5:31 PM

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