low beams not working - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Jwill41 · 11-19-2006, 05:20 PM

My low beam headlights stopped working. All four (GMC) work on high beam but nothing on low. Could this be the dimmer switch? It seems like I had this problem once before and it was the dimmer switch.

krue · 11-19-2006, 05:32 PM

Would be the first thing I would suspect.

Longhorn Man · 11-19-2006, 05:48 PM

yep... most likely. Try kicking it or turning it from high to low a few times.

Boise69 · 11-19-2006, 06:02 PM

Try moving the wires around near where they connect to the switch, mine does this too but i'm waiting for my new harness before i replace it. so once in awhile i have to wiggle em

Jwill41 · 11-19-2006, 06:13 PM

replaced the dimmer switch, still not working

Jwill41 · 11-19-2006, 06:37 PM

now i have also replaced the switch in the dash, still not working

89 crew · 11-19-2006, 06:38 PM

The first thing I would do is test the lights. make sure they work. just jump a hot with to it. since you have already replaced the dimmer switch, the problem has to be in the wires, unless the switch is bad. might try probing with a test light to make sure. after that it would have to be either a broken wire or corrision on the terminals.

Jwill41 · 11-19-2006, 06:52 PM

it puzzles me that they all four work on high beam. it seems like they wouldn't work at all if it were a bad connection.

Jwill41 · 11-19-2006, 08:02 PM

I just now figured it out.I put my foot in to push the dimmer switch and missed it. While pressing on the carpet they started working. I replaced the plug a few years ago and there is a bad connection at the splice. Man, that was buggin me.

**Palf70Step** · 11-19-2006, 08:23 PM

Aren't the lights dual element that are for low/high beam. Maybe the low beam is just zapped on both the outer bulbs.

Never mind...I didn't refresh the page and see you are Okie dokie now.

al's71gmc · 11-19-2006, 10:32 PM

Had the same problem on my son's truck. I didn't get it figured out by the time he took the truck off to college, so I ended up disconnecting the high beams. All he has is lows, but at least the cops won't ticket him for blinding people. I replaced the dimmer switch, no go. Searched for hours trying to figure how all 4 can work, but not the lows by themselves.

89 crew · 11-20-2006, 10:37 PM

The way the headlights work is one wire from the headlight switch. It goes to the dimmer switch and 2 wires go out from there. (one high beam one low. Same output voltage) the head lights will have either 2 or 3 connectors on each one will be ground the others hot. If 3 contacts on the lamp 2 hot 1 low beam, 1 high, 1 ground. If 2 contacts one high beam, one ground. Long as you keep it simple like that it is easy to diagnose. if any lights work you have power to the dimmer switch. If you then probe the dimmer and have power going out it has to be wires or bad lights.

11-19-2006, 05:20 PM	#1
Jwill41 Registered User Join Date: Aug 2002 Location: Farmers Branch, Tx Posts: 1,009	low beams not working My low beam headlights stopped working. All four (GMC) work on high beam but nothing on low. Could this be the dimmer switch? It seems like I had this problem once before and it was the dimmer switch. __________________ http://www.picturetrail.com/jwill41 67 1/2 ton GMC short step side 68 1/2 ton Chevy long fleet side 72 1/2 ton Chevy Suburban 99 1/2 ton Chevy Suburban founder (and only member) of the primer/clearcoat club

11-19-2006, 05:32 PM	#2
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	Re: low beams not working Would be the first thing I would suspect. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

11-19-2006, 05:48 PM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: low beams not working yep... most likely. Try kicking it or turning it from high to low a few times.

11-19-2006, 06:02 PM	#4
Boise69 The Hammer Man Join Date: Oct 2006 Location: Wilmington, NC Posts: 864	Re: low beams not working Try moving the wires around near where they connect to the switch, mine does this too but i'm waiting for my new harness before i replace it. so once in awhile i have to wiggle em

11-19-2006, 06:13 PM	#5
Jwill41 Registered User Join Date: Aug 2002 Location: Farmers Branch, Tx Posts: 1,009	Re: low beams not working replaced the dimmer switch, still not working __________________ http://www.picturetrail.com/jwill41 67 1/2 ton GMC short step side 68 1/2 ton Chevy long fleet side 72 1/2 ton Chevy Suburban 99 1/2 ton Chevy Suburban founder (and only member) of the primer/clearcoat club

11-19-2006, 06:37 PM	#6
Jwill41 Registered User Join Date: Aug 2002 Location: Farmers Branch, Tx Posts: 1,009	Re: low beams not working now i have also replaced the switch in the dash, still not working __________________ http://www.picturetrail.com/jwill41 67 1/2 ton GMC short step side 68 1/2 ton Chevy long fleet side 72 1/2 ton Chevy Suburban 99 1/2 ton Chevy Suburban founder (and only member) of the primer/clearcoat club

11-19-2006, 06:38 PM	#7
89 crew Registered User Join Date: Mar 2006 Location: Kansas Posts: 865	Re: low beams not working The first thing I would do is test the lights. make sure they work. just jump a hot with to it. since you have already replaced the dimmer switch, the problem has to be in the wires, unless the switch is bad. might try probing with a test light to make sure. after that it would have to be either a broken wire or corrision on the terminals.

11-19-2006, 06:52 PM	#8
Jwill41 Registered User Join Date: Aug 2002 Location: Farmers Branch, Tx Posts: 1,009	Re: low beams not working it puzzles me that they all four work on high beam. it seems like they wouldn't work at all if it were a bad connection. __________________ http://www.picturetrail.com/jwill41 67 1/2 ton GMC short step side 68 1/2 ton Chevy long fleet side 72 1/2 ton Chevy Suburban 99 1/2 ton Chevy Suburban founder (and only member) of the primer/clearcoat club

11-19-2006, 08:02 PM	#9
Jwill41 Registered User Join Date: Aug 2002 Location: Farmers Branch, Tx Posts: 1,009	Re: low beams not working I just now figured it out.I put my foot in to push the dimmer switch and missed it. While pressing on the carpet they started working. I replaced the plug a few years ago and there is a bad connection at the splice. Man, that was buggin me. __________________ http://www.picturetrail.com/jwill41 67 1/2 ton GMC short step side 68 1/2 ton Chevy long fleet side 72 1/2 ton Chevy Suburban 99 1/2 ton Chevy Suburban founder (and only member) of the primer/clearcoat club

11-19-2006, 08:23 PM	#10
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 46,845	Re: low beams not working Aren't the lights dual element that are for low/high beam. Maybe the low beam is just zapped on both the outer bulbs. Never mind...I didn't refresh the page and see you are Okie dokie now. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God! Last edited by Palf70Step; 11-19-2006 at 08:24 PM.

11-19-2006, 10:32 PM	#11
al's71gmc 4 eyed fever Join Date: Jul 2005 Location: Eureka, Nevada Posts: 500	Re: low beams not working Had the same problem on my son's truck. I didn't get it figured out by the time he took the truck off to college, so I ended up disconnecting the high beams. All he has is lows, but at least the cops won't ticket him for blinding people. I replaced the dimmer switch, no go. Searched for hours trying to figure how all 4 can work, but not the lows by themselves. __________________ 1971 GMC 2500 4x4 1972 GMC Sierra Grande 1/2 t 4x4-#1 son's truck. Recently completed resto. 4 YO daughter," Daddy, I like your truck better than Mom's." (2000 F350-ranch truck) Smart kid!!

11-20-2006, 10:37 PM	#12
89 crew Registered User Join Date: Mar 2006 Location: Kansas Posts: 865	Re: low beams not working The way the headlights work is one wire from the headlight switch. It goes to the dimmer switch and 2 wires go out from there. (one high beam one low. Same output voltage) the head lights will have either 2 or 3 connectors on each one will be ground the others hot. If 3 contacts on the lamp 2 hot 1 low beam, 1 high, 1 ground. If 2 contacts one high beam, one ground. Long as you keep it simple like that it is easy to diagnose. if any lights work you have power to the dimmer switch. If you then probe the dimmer and have power going out it has to be wires or bad lights.

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