Headlight Issue-wiring - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 10-14-2019, 09:19 PM Thread Starter
 
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Headlight Issue-wiring

70 GTO...putting the pieces back together after a botched restoration effort by a so called expert. Anyway, I reinstalled the dash and plugged it all together. When I pulled the light switch the passenger side low beam works. The drivers side the low beam is very dim and there seams to be a voltage bleed to the high beam as there is a faint glow from that headlight too. I hit the dimmer switch and no high beams at all. All other lights are functional. Directionals, parking, and rear lights work fine.
Before I pull the nose off and start replacing harnesses, does anyone have any ideas on where to start a trouble shooting effort?
Any help for this neophyte would be appreciated.
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post #2 of 9 (permalink) Old 10-14-2019, 09:47 PM
 
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Originally Posted by PatrickM View Post
70 GTO...putting the pieces back together after a botched restoration effort by a so called expert. Anyway, I reinstalled the dash and plugged it all together. When I pulled the light switch the passenger side low beam works. The drivers side the low beam is very dim and there seams to be a voltage bleed to the high beam as there is a faint glow from that headlight too. I hit the dimmer switch and no high beams at all. All other lights are functional. Directionals, parking, and rear lights work fine.
Before I pull the nose off and start replacing harnesses, does anyone have any ideas on where to start a trouble shooting effort?
Any help for this neophyte would be appreciated.
Check and see if you have loose grounds behind the headlight/grill somewhere.
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post #3 of 9 (permalink) Old 10-15-2019, 12:59 PM
 
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dimmer switches are known to fail also
and make your headlight act funny
usually they default to no brites in my cases of failure

good clean grounds

unplug the other light,,,?

swap bulbs ?

Scott
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post #4 of 9 (permalink) Old 10-15-2019, 08:06 PM Thread Starter
 
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Thanks. Iíll start with grounds and then move on from there.
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post #5 of 9 (permalink) Old 10-15-2019, 08:35 PM
 
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After the grounds i would pull the light switch and test voltage for the outputs...

Lighting systems on these old cars are pretty easy. Start with the switch and work your way back. The head light power has to go thru the high beam switch as well so test the voltage there next...

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #6 of 9 (permalink) Old 10-16-2019, 11:49 AM Thread Starter
 
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Thanks...just installed the dash...i should be able to get to the light switch without pulling the entire dash out again. Iíll try that as well. Appreciate your response.
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post #7 of 9 (permalink) Old 10-16-2019, 12:53 PM
 
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I agree, Definitely a ground problem and feeding back thru the circuit.
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post #8 of 9 (permalink) Old 10-17-2019, 08:47 AM
 
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I believe there is a the ground backet behind the light switch and wiper bracket. If you want to try a new lightswitch, I bought one at a napa store but I had to ask for one for a 70 chevelle because nothing came up for Gto.
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post #9 of 9 (permalink) Old 10-17-2019, 07:12 PM
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Sounds like the headlight itself is mis-wired. Either the high or low beam wires are on the ground wire terminal and are now back feeding through the high beam bulb looking for a ground. Found this photo on another site. Check to make sure the low beam bulbs are wired correctly.
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Ed


68 GTO (Thanks Mom)
70 El Camino SS
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring

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