Headlight Harness MOD
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Joined: Sep 2001
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Headlight Harness MOD
The modification I am referring to is the harness with relays. LMC and Summit etc sell it. This is so the headlights get near full power because the power isn't running through the headlight switch. I have searched but didn't really get the answer I was hoping for.
I am curious if the added voltage could cause premature headlight bulb failure or added heat to the headlight housing. I was just intrested in any potential problems with this modification.
Does anyone have this done on their 92-96 truck?
For any interested, I have Sylvania Xtravision bulbs and they do make a difference. We put GE Nighthawk bulbs in my Dad's 97 Cobra and they made an improvement also. I think the Nighthawks may be brighter than the Xtras, but don't know for sure since they are in different vehicles.
I am curious if the added voltage could cause premature headlight bulb failure or added heat to the headlight housing. I was just intrested in any potential problems with this modification.
Does anyone have this done on their 92-96 truck?
For any interested, I have Sylvania Xtravision bulbs and they do make a difference. We put GE Nighthawk bulbs in my Dad's 97 Cobra and they made an improvement also. I think the Nighthawks may be brighter than the Xtras, but don't know for sure since they are in different vehicles.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Good point. What does the bulb manufacturer say about bulb life under these conditions? I suspect the bulbs are rated for the typical automotove charge voltage of about 13.5v but better to get it from the horses mouth. I like the idea of running the headlights through a relay, it makes a lot of sense for several reasons, it opens the door to automatic light control. The whole lighting system on my Subaru is setup this way, doesn't matter where the switches are set, all the lights shut of when you remove the key.
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I think it makes sense as well.
Both the Nighthawk and the Xtravision say that they are 12 volt bulbs. I don't know if there is actual specs available for them.
As far as the mod goes, I have heard people say that they only get about 10-11 volts at the bulbs, with the OEM setup, and after the mod is installed they get 12 or more volts at the bulbs.
I just thought that if it was designed one way to start with then changing it could cause a problem.
Both the Nighthawk and the Xtravision say that they are 12 volt bulbs. I don't know if there is actual specs available for them.
As far as the mod goes, I have heard people say that they only get about 10-11 volts at the bulbs, with the OEM setup, and after the mod is installed they get 12 or more volts at the bulbs.
I just thought that if it was designed one way to start with then changing it could cause a problem.
Lead Driver
Joined: Aug 2006
Posts: 5,670
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From: Sand Lake, MI
Had they wired the truck right to start with, not run the circuit through the headlight switch the bulbs would get the right voltage to start with. A melting switch/harness can't be what they had in mind to limit/control the voltage to the bulbs!
Just plain bad engineering.
In my 94 the switch is dieing/dead melting yet again, I'm going with the relay setup and being done with it. About as easy to setup as repairing the system as is again.
Bulbs are made for a vehicle with a 12v system, so they rate em "12v". They know the voltage is actually higher then that on a "running" vehicle.
Heck a "good" battery by itself has slightly more volts then that.
Just plain bad engineering.
In my 94 the switch is dieing/dead melting yet again, I'm going with the relay setup and being done with it. About as easy to setup as repairing the system as is again.
Bulbs are made for a vehicle with a 12v system, so they rate em "12v". They know the voltage is actually higher then that on a "running" vehicle.
Heck a "good" battery by itself has slightly more volts then that.
Mountain Pass
Joined: Oct 2007
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From: Falls of Rough, KY
I have the Summit APC kits on my 93 Lightning, and 94 4x4, and they work great. I burnt up 2 headlight switches in my 94 4x4 by running the zeon bulbs. Now I have bright lights, and no switch problems, and no bulb problems. Most of my driving is with lights on, as I work 2nd shift. I do not drive the trucks everyday, but have had the kits installed for 4, or 5 years on the 94.
Lead Driver
Joined: Nov 2002
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From: Concord, NC
Just plain bad engineering.
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I looked up the specs and both bulbs are rated for 12.8 volts. I may end up doing this at some point.
I read about the burned up headlight switches. It seems to me that if they designed it this way they should have used a heavier duty switch. Mine is still original though.
I read about the burned up headlight switches. It seems to me that if they designed it this way they should have used a heavier duty switch. Mine is still original though.
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Posting Guru
Joined: May 2007
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From: North Reading Mass
My old 83 burned up a couple of headlight switches and it turned out to be bad connections causing high resistance. Ford isn't the only one to have this problem and the headlight relay Mod shows up in many car and truck forums. BTW if the bulbs are rated for 12v it will be fine at 13.8v. As the voltage goes up the amps go down but watts remains the same.
regards
rikard
regards
rikard
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I have the Summit APC kits on my 93 Lightning, and 94 4x4, and they work great. I burnt up 2 headlight switches in my 94 4x4 by running the zeon bulbs. Now I have bright lights, and no switch problems, and no bulb problems. Most of my driving is with lights on, as I work 2nd shift. I do not drive the trucks everyday, but have had the kits installed for 4, or 5 years on the 94.
The only relay kit I can find is the one on LMC.
I wonder if one is any better than the other.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Yeah... if you want to see a vehicle with wiring so undersized the headlights only get about 1/2 voltage look for one of those mid '90's Plymouth/Dodge Duster or Sundance. A friend of mine has one and we couldn't believe how useless the headlights were so we rewired it with a relay direct to the battery, the differece was literally night and day. 
Elder User
Joined: Feb 2002
Posts: 636
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From: Portage Twp, PA
Well, I don't think running full battery voltage to the headlights will shorten the life of the bulb, but perhaps running less than full voltage may lengthen the life. But then again, maybe not...some electrical components tend to lead shorter lives if they're underpowered. I'm not sure if a light bulb is in that category, though.
I think it boils down to this: would you rather have a long-lasting bulb, or would you rather be able to SEE at night? I've never had an issue with the headlights in my '89, but I've had all the parts for the relay upgrade lying around for months...reckon I've put it off long enough!
Pat
I think it boils down to this: would you rather have a long-lasting bulb, or would you rather be able to SEE at night? I've never had an issue with the headlights in my '89, but I've had all the parts for the relay upgrade lying around for months...reckon I've put it off long enough!
Pat