Another help ? ...tailights broke - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ftw80 · 10-25-2003, 03:34 PM

I checked previous posts and could not find the same symptoms. My lights all seem to work except tail lights. The rear blinkers are working but no rear runiing lights or rear side markers. I had the truck apart to paint and I am sure I unhooked something. Any suggestions? thx

BLACK AND BLUE 67-72 · 10-25-2003, 03:40 PM

Check your grounds and wiring. It could also be in your light switch.

Green72GMC · 10-25-2003, 05:25 PM

Check where the lights plug in, in the rear of the truck. Mine did that a while back and the plug just came loose.

71GMC_3/4T · 10-25-2003, 05:31 PM

Your taillights share the same fuse with the dash lights. Do your dash lights work?

If the rear blinkers work, I assume the brake lights work as they use the same half of the filament. If the brake/turn lights work, your ground should be okay, but bad grounds can cause strange things to happen. Check to see if you have voltage first.

The brown colored wire going from the firewall to the taillights is the park lights. It should be a group of 4, with light and dark green and yellow. Yellow is left, and dark green is right, and light green is reverse lights. They're usually a ribbon of 4 wires, located just above your throttle cable. Use a pointy exact knife blade to slightly pierce the insulation and check with a voltmeter referenced to chassis. Whether or not you have voltage at the firewall will tell you which way to go look for it. Much easier than pulling the taillight housings to look for something that may not be a problem.

Good Luck and let us know what you find. I imagine someone else will be noticing problems with taillights now that the time will change, and maybe you can save them (and me, possibly) some time.

ftw80 · 10-26-2003, 04:57 AM

dash lights work...but I dont have brake lights. I am still putting things back so I hope to find the problem. Does the circuit baord have anything to do with tail lights? Gas gauge is reading way over full but I do not have one tank installed.

Thx for the pointers and I will post when I figure it out.

A.P. · 10-26-2003, 06:45 AM

I had a similar problem with my truck when it was painted. It turned out to be the groundings for each individual light. I used a multimeter to trace for good grounds and voltage. These diagrams were a big help.

http://www.geocities.com/chevroletc1070/wiringdias.html

71GMC_3/4T · 10-26-2003, 11:29 AM

No brake lights? Could be several things, but I'd check the following: Brake light Switch, just above the brake pedal. 4-way flasher on the fuse panel. 4-way (hazard) switch on the side of the steering column at the turn signal switch (should be "out" for normal operation). And your brake light fuse.

10-25-2003, 03:34 PM	#1
ftw80 Registered User Join Date: Feb 2000 Location: hawaii Posts: 268	Another help ? ...tailights broke I checked previous posts and could not find the same symptoms. My lights all seem to work except tail lights. The rear blinkers are working but no rear runiing lights or rear side markers. I had the truck apart to paint and I am sure I unhooked something. Any suggestions? thx __________________ Haleiwa, Hi. 1972 Custom Camper Cheyenne Super c/20 Longhorn 402bb 78k a/c, tach, tilt, tool stowage 48panhead 74 bronco 71 bronco http://noscade.com No Scade is pidgin English for "not scared" similar to "no fear".

10-25-2003, 03:40 PM	#2
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Check your grounds and wiring. It could also be in your light switch. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA

10-25-2003, 05:25 PM	#3
Green72GMC Registered User Join Date: Apr 2003 Location: Deville, Louisiana Posts: 293	Check where the lights plug in, in the rear of the truck. Mine did that a while back and the plug just came loose. __________________ 1972 GMC SWB, 305 powered 1980 diesel VW pickup, Needs a Heart Transplant 1997 Toyota Taco The Second Amendment is in place incase they ignore the others.

10-25-2003, 05:31 PM	#4
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	Your taillights share the same fuse with the dash lights. Do your dash lights work? If the rear blinkers work, I assume the brake lights work as they use the same half of the filament. If the brake/turn lights work, your ground should be okay, but bad grounds can cause strange things to happen. Check to see if you have voltage first. The brown colored wire going from the firewall to the taillights is the park lights. It should be a group of 4, with light and dark green and yellow. Yellow is left, and dark green is right, and light green is reverse lights. They're usually a ribbon of 4 wires, located just above your throttle cable. Use a pointy exact knife blade to slightly pierce the insulation and check with a voltmeter referenced to chassis. Whether or not you have voltage at the firewall will tell you which way to go look for it. Much easier than pulling the taillight housings to look for something that may not be a problem. Good Luck and let us know what you find. I imagine someone else will be noticing problems with taillights now that the time will change, and maybe you can save them (and me, possibly) some time. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO Last edited by 71GMC_3/4T; 10-26-2003 at 11:25 AM.

10-26-2003, 04:57 AM	#5
ftw80 Registered User Join Date: Feb 2000 Location: hawaii Posts: 268	dash lights work...but I dont have brake lights. I am still putting things back so I hope to find the problem. Does the circuit baord have anything to do with tail lights? Gas gauge is reading way over full but I do not have one tank installed. Thx for the pointers and I will post when I figure it out. __________________ Haleiwa, Hi. 1972 Custom Camper Cheyenne Super c/20 Longhorn 402bb 78k a/c, tach, tilt, tool stowage 48panhead 74 bronco 71 bronco http://noscade.com No Scade is pidgin English for "not scared" similar to "no fear".

10-26-2003, 06:45 AM	#6
A.P. Black 72 Chevy Join Date: May 2002 Location: Los Angeles, California Posts: 662	I had a similar problem with my truck when it was painted. It turned out to be the groundings for each individual light. I used a multimeter to trace for good grounds and voltage. These diagrams were a big help. http://www.geocities.com/chevroletc1070/wiringdias.html

10-26-2003, 11:29 AM	#7
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	No brake lights? Could be several things, but I'd check the following: Brake light Switch, just above the brake pedal. 4-way flasher on the fuse panel. 4-way (hazard) switch on the side of the steering column at the turn signal switch (should be "out" for normal operation). And your brake light fuse. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO



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