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Headlight Wiring

TX63CONV

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Joined
Sep 14, 2010
Messages
316
Location
Dallas, TX
I am wiring a 69 mustang and have an issue with my headlights. I think I have voltage leakage to the two inner high beams.

When the outer low beams are on, there is a faint glow on the high beams. This is all new wiring, new high beam switch. I drilled two new holes into the core support for the ground wires on each side. I was able to ground my battery and get 12.8v at each screw so I DONT THINK it is the ground to the body.

When I remove the ground from the drivers side of the body, the high beam on the psgr side comes on and vice versa.

Is there a way to systematically check where the issue is?
 
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justsam

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Aug 20, 2010
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1,271
Location
Penngrove, California
Sounds like it is finding ground thru the high beam filament. Indicates to me you do not have a proper ground at the low beam bucket. If you remove high beam bulbs, do the low beams not work at all?
 

BFBOB

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Joined
Sep 20, 2011
Messages
5,073
All new wiring, sockets included?
Check with an ohmmeter to make sure you know which wire on the bulb sockets goes to the Hi, Lo, and common. I've found sockets with the colors of the wires in different places, so matching colors to the old sockets doesn't guarantee correct wiring. Make sure that the common wire goes to ground, then it's pretty easy to sort out which wires go to hibeam and lobeam.
 

ktmracer

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Joined
Mar 6, 2012
Messages
47
Location
Fresno area
Be sure to consider the MAD style of wiring your headlights. It may fix your issue and your lights will much brighter. (Relays, less amps thru the switch,etc)
 

astroracer

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Jun 22, 2005
Messages
3,001
Location
Mid_Michigan
Be sure to consider the MAD style of wiring your headlights. It may fix your issue and your lights will much brighter. (Relays, less amps thru the switch,etc)

Ditto on the statement above. Go here and do some reading.
http://madelectrical.com/electricaltech/brighter-headlights.shtml
Very enlightening. And make sure your "core support" is grounded to the frame/engine block/negative terminal. During rebuilds many "ground cables" get lost. Grounds are a necessary and very important part of the electrical system as I think you will find out.
Also, just drilling holes and adding a bolt is not good. You need to grind off the paint and use star washers to get a good bite into the metal to make a good ground connection.
Mark
 
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2Big2Ride

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Joined
Oct 24, 2010
Messages
258
Location
d/FW, Texas - more FW than D
When you see another bulb or filament with a dull glow it is a sign of a bad ground. Try a jumper from the light's ground to the negative post on the battery and then also the ground on the core support to see if it solves the problem. If it does, you know you have to work on improving the ground at the core support.
 

egnorant

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May 2, 2012
Messages
1,805
Location
East Texas
I had a problem with my headlights (and running light and turn indicators). My fix was to insure a good ground for the front bumper!! What I think was happening was that the running/clearance lights were pulling a ground through the headlights.

After making everything pretty with paint and polish, I reassembled and my front bumper ground was bad. After getting it back to stock, I still ran a good solid ground wire to the bumper bracket and installed a relay setup for the headlights. 11 years and no problems!

Bruce
 
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TX63CONV

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Joined
Sep 14, 2010
Messages
316
Location
Dallas, TX
Make sure the prongs on the headlight go to the correct wire.

I became painfully aware on a '40 Ford that the prongs aren't laid out like you'd think they should be.

Thanks for all the replies. I finally found a diagram in which I had the ground and the high beam reversed in the three prong plug. Switched them on both sides and works like a champ.

Thanks everyone for the links and insight.
 
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