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Old 10-31-2010, 08:16 AM
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Dim low beam headlights

I have a problem with my 56 Ford sedan delivery. The headlights on low beams are dim. On high they are just like they should be. It has a Ron Francis wiring kit that I installed. The headlights are GE halogen sealed beams. I have swapped out a known set out of another rig that were working fine. The ones out of the delivery are in that rig and they work fine and are not dim. This eliminates bad bulbs. My question is what do I check and how? I don't know if it makes a difference but it has a GM 1 wire alternator and all other lights, turn signals and accessories work great.
Thanks!
Bill

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Old 10-31-2010, 08:27 AM
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Sounds to me like it could be a bad ground. Or maybe the dimmer switch you are getting feed to the switch though or the brights wouldn't work properly as they are. I would check the wires at the dimmer switch and go from the dimmer low side check the wires up to the headlights. Also what alternator set-up are you using? Sometime when running a one wire set-up it can cause some similar problems too. JMO


Cole
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Old 10-31-2010, 08:31 AM
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If you have access to a volt ohm meter check the voltage at the bulbs when they are are on low beam. FWIW even the Ron francis wiring kit may require relays to properly supply the current needed for halogen bulbs.

Vince
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Old 10-31-2010, 09:34 AM
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Vince
The Francis kit does have a headlight relay and it did the same thing with standard headlights before I put in the Halogens. With the standards I thought the bulbs were just old. I will check the voltage on low.
Cole
I have replaced the dimmer switch as I thought it might be the culprit. No change! I will check the voltage at the dimmer and at the headlight tomorrow. I don't know what 1 wire it is as I just went to the parts store and bought one. I don't know how this grounds. Is one of the 3 wires on the headlights a ground?
Bill
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Old 10-31-2010, 10:53 AM
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wiring error

Since you have eliminated the common causes the only thing left is a wiring error.
Check the headlamp plugs for correct connections.
Facing the back of the lamp the top single connector is the low beam.
The left side connector is the ground.
The right side connector is the high beam.
What you have is the ground is connected to the high beam connector on the lamp, the high beam wire is connected to the ground connector on the lamp, the low beam wire is connected to the low beam connector on the lamp.
When you switch to high beam you have a circuit to ground thou the high beam filament.
When you switch to low beam the high and low beam filaments are now in series and 12 volts is now dropped across both filaments which accounts for the dim light.

vicrod
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Old 10-31-2010, 11:04 AM
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Thanks I'll check this out and let you know what I find!
Bill
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Old 10-31-2010, 11:31 AM
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Quote:
Originally Posted by ogrebro
Is one of the 3 wires on the headlights a ground?
Bill

Yes; one of the wires is a ground black usually; one wire low beam; one wire high beam

If you did not have a ground no lights would work; low beams are dim and the highs are ok; the problem in is the low beam circuit. You say you changed the dimmer; compare the voltage reading coming off the dimmer too the low beam; then go to the head light and take the reading there; should be the same. However dim low beams says it will read lower.

More to consider; the next item to check is the wiring itself; beyond the dimmer switch it is pretty much a straight run of wire, I am not acquainted with how the truck is set up, but if the next stop from the dimmer is a firewall plug look at that. Somewhere the headlight wiring L & R is tied together to become a one wire feed and then ends up a single plug on the dimmer.

The connection of the joined wires if crimped could be worth a look. If there is a firewall plug large square type the pins may be not seated. I would not suggest opening the whole plug, you could id the low beam wire and just push on it a bit to make sure it is in. These are few things to look for that could cause a voltage drop.

vicrod makes a good case that shows how the voltage drop could be happening; that would be the simplest and most probable scenario.

Last edited by pepi; 10-31-2010 at 11:37 AM.
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Old 10-31-2010, 03:53 PM
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Vicrod you are a genius!!!! You were absolutely correct. I changed the wires in the plug and they work as advertised!
I cannot thank you enough. It's always the simple things that bite you in the *****.Thanks again!
Bill
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Old 10-31-2010, 05:51 PM
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Glad you got it fixed.


Cole
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Old 10-31-2010, 06:06 PM
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Happy to help.

vicrod
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