No high beams :( - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**SOON2BLAZE** · 01-18-2011, 09:55 PM

A few years ago I installed the headlight harness that classic industries sells to get more power to my gmc four eye headlights. On the way home the other night I hit my floor switch to kick on the high beams and SUPRISE.. no headlights at all. When I hit the switch again the low beams came back on. All connections are good, had some new high beams in the garage so I installed them...nothing. Wondering if it's one of the relays in the aftermarket harness. Any thoughts?

Sillyoldman · 01-18-2011, 10:03 PM

I've had the same issues with a bad dimmer switch.

swamp rat · 01-18-2011, 10:03 PM

Is there any inline fuse blocks within the power wiring to the relays? start there.

nonamecharlie · 01-18-2011, 10:06 PM

I had that problem on one headlight, turned out to be just a bad connection on the back of the headlight.

danleaman · 01-18-2011, 10:13 PM

my 72 C-20 did the same thing, a new dimmer switch fixed it.

Longhorn Man · 01-18-2011, 10:16 PM

I would start with turning on the highbeams, and kicking the switch, like from the side.
If nothing happens, then I would swap the two fuses and see if you have high and no low
If you still don't have highbeams, you need to start troubleshooting with a test light

**SOON2BLAZE** · 01-18-2011, 10:44 PM

Quote:

Originally Posted by Longhorn Man

I would start with turning on the highbeams, and kicking the switch, like from the side.
If nothing happens, then I would swap the two fuses and see if you have high and no low
If you still don't have highbeams, you need to start troubleshooting with a test light

Good idea. The reason I think the dimmer switch is still good is it still turns my high beam indicator light on in the speedo.

oldblue1968chevy · 01-18-2011, 11:25 PM

Mine did the same thing, bad dimmer switch.

Longhorn Man · 01-18-2011, 11:28 PM

high beam light in the dash comes on then the switch is doing its job. Go directly to the relay

67chevy1series · 01-18-2011, 11:35 PM

my dad has that key word has

**VetteVet** · 01-18-2011, 11:46 PM

You've got three wires going to the dimmer switch. The blue is the power wire from the headlight and has power any time the headlight switch is on. All you need to do is jumper the blue wire to the tan wire and see if you get any lights. Then jumper the green and blue wires and see if the lights come on. If you get lights when jumping both wires then the dimmer switch is bad on the high beam side. If you only get lights when jumping one of the wires then the problem is under the hood.

You may have burned out a relay or lost the ground to it. I have a diagram of the GMC headlight relay mod so if it isn't the dimmer switch then I'll post up the diagram .

**SOON2BLAZE** · 01-18-2011, 11:54 PM

Nailed it Andy. Swapped relays and they both worked. Small amount of corrosion noted in one of them. Thanks to all for your replys!

*198ChevyGuy* · 01-19-2011, 05:53 AM

What would it be if your high beam indicator on dash is on in either position? but when i go to click the high beams i lose my passenger side headlight

71LWBFS · 01-30-2011, 05:26 PM

Thought I had same problem about a week ago I lost my highbeams, swapped in silverstars I already had and still no highs. So I started to do as vettevet said and pulled wire plug off of floor switch and as I proceeded to test the
I noticed that the housing had melted/broken/been ground down so that the highbeam (green i think)wire/connector was grounding out on the floor :/ I wrapped the plug housing with electrical tape to insulate it and it's all good now

Posted via Mobile Device

01-18-2011, 09:55 PM	#1
SOON2BLAZE Account Suspended Join Date: Aug 2005 Location: Southern UT Posts: 906	No high beams :( A few years ago I installed the headlight harness that classic industries sells to get more power to my gmc four eye headlights. On the way home the other night I hit my floor switch to kick on the high beams and SUPRISE.. no headlights at all. When I hit the switch again the low beams came back on. All connections are good, had some new high beams in the garage so I installed them...nothing. Wondering if it's one of the relays in the aftermarket harness. Any thoughts?

01-18-2011, 10:03 PM	#2
Sillyoldman #16876 Join Date: Apr 2005 Location: Auburn WA Posts: 12,266	Re: No high beams :( I've had the same issues with a bad dimmer switch. __________________ Posted via Stationary Device '71 Custom Deluxe C-20 402. '67 Buick Special 455. '49 Plymouth Special Deluxe. *"I love that old car smell"* *Some people are like Slinkies... not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.*

01-18-2011, 10:03 PM	#3
swamp rat Registered User Join Date: Oct 2007 Location: Spanaway Posts: 8,451	Re: No high beams :( Is there any inline fuse blocks within the power wiring to the relays? start there. __________________ Mike. Swamp Rat build thread : http://67-72chevytrucks.com/vboard/s...d.php?t=595019 72 3/4T 4X4 4" BDS Lift 33" BFG's

01-18-2011, 10:06 PM	#4
nonamecharlie Registered User Join Date: Mar 2010 Location: Felton, CA Posts: 18	Re: No high beams :( I had that problem on one headlight, turned out to be just a bad connection on the back of the headlight. __________________ 1971 Chevy C20 Camper Special 350 V8

01-18-2011, 10:13 PM	#5
danleaman Registered User Join Date: Jul 2010 Location: Las Vegas, Nevada Posts: 43	Re: No high beams :( my 72 C-20 did the same thing, a new dimmer switch fixed it.

01-18-2011, 10:16 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: No high beams :( I would start with turning on the highbeams, and kicking the switch, like from the side. If nothing happens, then I would swap the two fuses and see if you have high and no low If you still don't have highbeams, you need to start troubleshooting with a test light

01-18-2011, 11:25 PM	#8
oldblue1968chevy Grandpa in the rustmobile... Join Date: Nov 2008 Location: Spokane WA/Viola TN Posts: 11,422	Re: No high beams :( Mine did the same thing, bad dimmer switch. __________________ John Goose-1968 C10 355,9.32-1CR, Vortec Heads ,262 voodoo, 3.73:1 3OTT (HS ride/beater/farm truck) http://67-72chevytrucks.com/vboard/s...d.php?t=317684 Grams 53-1953 Chevrolet Belair http://67-72chevytrucks.com/vboard/s...=1#post4327784 1969 Chevy C10 Shortbed 4.5/6?" Frame off resto http://67-72chevytrucks.com/vboard/s...d.php?t=548136 1999 Toyota Tacoma 4x4

01-18-2011, 11:28 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: No high beams :( high beam light in the dash comes on then the switch is doing its job. Go directly to the relay

01-18-2011, 11:35 PM	#10
67chevy1series Registered User Join Date: Mar 2010 Location: a t w a t e r cali 95301 Posts: 10,713	Re: No high beams :( my dad has that key word has

01-18-2011, 11:46 PM	#11
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,719	Re: No high beams :( You've got three wires going to the dimmer switch. The blue is the power wire from the headlight and has power any time the headlight switch is on. All you need to do is jumper the blue wire to the tan wire and see if you get any lights. Then jumper the green and blue wires and see if the lights come on. If you get lights when jumping both wires then the dimmer switch is bad on the high beam side. If you only get lights when jumping one of the wires then the problem is under the hood. You may have burned out a relay or lost the ground to it. I have a diagram of the GMC headlight relay mod so if it isn't the dimmer switch then I'll post up the diagram . __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

01-18-2011, 11:54 PM	#12
SOON2BLAZE Account Suspended Join Date: Aug 2005 Location: Southern UT Posts: 906	Re: No high beams :( Nailed it Andy. Swapped relays and they both worked. Small amount of corrosion noted in one of them. Thanks to all for your replys!

01-19-2011, 05:53 AM	#13
198ChevyGuy Account Suspended Join Date: Jan 2011 Location: Midwest City, Oklahoma Posts: 85	Re: No high beams :( What would it be if your high beam indicator on dash is on in either position? but when i go to click the high beams i lose my passenger side headlight

01-30-2011, 05:26 PM	#14
71LWBFS Registered User Join Date: Dec 2010 Location: Dixon, CA Posts: 5	Re: No high beams :( Thought I had same problem about a week ago I lost my highbeams, swapped in silverstars I already had and still no highs. So I started to do as vettevet said and pulled wire plug off of floor switch and as I proceeded to test the I noticed that the housing had melted/broken/been ground down so that the highbeam (green i think)wire/connector was grounding out on the floor :/ I wrapped the plug housing with electrical tape to insulate it and it's all good now Posted via Mobile Device



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