headlight problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

modifiedGMC · 10-29-2005, 10:43 AM

I got my relays mounted and ready to hook to the headlights BUT I got a slight problem first. I got a 69 GMC with four headlights, halogens to be specific, when I have them on bright all is just fine. When I put them on dim the two outer light are on like they are supposed to be but not as bright as they should be and the two inner lights can be seen barely glowing when they shouldn't be. I thought bad grounds , so I took the grounds loose and cleaned them to the bare metal... Didn't help. so I tried cleaning the terminals on the sockets and bulbs... didn't help. BUT while I had one of the inner bulbs out I took a piece of wire and stuck it down in the socket on the ground side then touched it to ground with the dim lights on .... no help. Then I took that same piece of wire and touched it from the ground side of the socket over to the other side of the socket and the two dim lights got brighter like they should be and the other dim light wasn't glowing. Does any body have an idea what could cause this? should I go ahead and wire up the relays and take a 50/50 chance that it could solve the problem?

**Stocker** · 10-29-2005, 11:28 AM

Strictly a guess.... bad dimmer switch?

**clay68c10** · 10-29-2005, 11:33 AM

It seems like you may have righ resistance somewhere, causing the current to bleed back thru where you don't want it. How are all the connections, terminals, and such? Are they all soldered? I would say one of your connections or switches is funky.

modifiedGMC · 10-29-2005, 07:58 PM

Quote:

Originally Posted by Stocker

Strictly a guess.... bad dimmer switch?

That is a possibility. it's not been replaced for several years(like 8 yrs or so). I do remember back about 1997 or 98 I always ran with them on dim because the wires to the dimmer would get real hot on bright but not dim.

GMC Jim · 10-29-2005, 08:20 PM

when the relays are wired in.... the dimmer switch controls the relays for the required hi/low beam switching. If the dimmer switch selects the hi/low function; then the deiimer switch would be Ok.

**Stocker** · 10-29-2005, 08:20 PM

Well - personally, I'd prefer to find & fix the problem before adding to/changing the wiring (relays). However, if it gets too frustrating, I would probably hook up the new stuff just in case that does fix - er, I meant bypass - the problem!

modifiedGMC · 10-29-2005, 10:13 PM

The dimmer switch does change them from bright to dim, it's just they have the problem mentioned above. Like I said, I've cleaned the bulb terminals, the plug terminals, both ground connections so it has to be some where in the wiring or the switch or the dimmer. I guess I could just go ahead and wire the relays in, If it still does it then I'll have to go from there. If it doesn't do it then I can say "what problem?"

Longhorn Man · 10-29-2005, 10:48 PM

Have you tried running a ground from the battery to the rad core support?
The back feeding is a classic bad ground indicator, and there is a chance that your ground strap has been torn or is missing all together.

10-29-2005, 10:43 AM	#1
modifiedGMC Registered User Join Date: Oct 2004 Location: Walker Co. Alabama Posts: 474	headlight problem I got my relays mounted and ready to hook to the headlights BUT I got a slight problem first. I got a 69 GMC with four headlights, halogens to be specific, when I have them on bright all is just fine. When I put them on dim the two outer light are on like they are supposed to be but not as bright as they should be and the two inner lights can be seen barely glowing when they shouldn't be. I thought bad grounds , so I took the grounds loose and cleaned them to the bare metal... Didn't help. so I tried cleaning the terminals on the sockets and bulbs... didn't help. BUT while I had one of the inner bulbs out I took a piece of wire and stuck it down in the socket on the ground side then touched it to ground with the dim lights on .... no help. Then I took that same piece of wire and touched it from the ground side of the socket over to the other side of the socket and the two dim lights got brighter like they should be and the other dim light wasn't glowing. Does any body have an idea what could cause this? should I go ahead and wire up the relays and take a 50/50 chance that it could solve the problem? __________________ If it don't fit, force it,...If it still don't fit , modify it 'till it does fit !!!

10-29-2005, 11:28 AM	#2
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,582	Re: headlight problem Strictly a guess.... bad dimmer switch? __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

10-29-2005, 11:33 AM	#3
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,932	Re: headlight problem It seems like you may have righ resistance somewhere, causing the current to bleed back thru where you don't want it. How are all the connections, terminals, and such? Are they all soldered? I would say one of your connections or switches is funky. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

10-29-2005, 08:20 PM	#5
GMC Jim Senior Member Join Date: Dec 2002 Location: Portland, Oregon Posts: 901	Re: headlight problem when the relays are wired in.... the dimmer switch controls the relays for the required hi/low beam switching. If the dimmer switch selects the hi/low function; then the deiimer switch would be Ok. __________________ '71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal).

10-29-2005, 08:20 PM	#6
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,582	Re: headlight problem Well - personally, I'd prefer to find & fix the problem before adding to/changing the wiring (relays). However, if it gets too frustrating, I would probably hook up the new stuff just in case that does fix - er, I meant bypass - the problem! __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

10-29-2005, 10:13 PM	#7
modifiedGMC Registered User Join Date: Oct 2004 Location: Walker Co. Alabama Posts: 474	Re: headlight problem The dimmer switch does change them from bright to dim, it's just they have the problem mentioned above. Like I said, I've cleaned the bulb terminals, the plug terminals, both ground connections so it has to be some where in the wiring or the switch or the dimmer. I guess I could just go ahead and wire the relays in, If it still does it then I'll have to go from there. If it doesn't do it then I can say "what problem?" __________________ If it don't fit, force it,...If it still don't fit , modify it 'till it does fit !!!

10-29-2005, 10:48 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: headlight problem Have you tried running a ground from the battery to the rad core support? The back feeding is a classic bad ground indicator, and there is a chance that your ground strap has been torn or is missing all together.



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