74 F250 headlight problem
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From: Dolan Springs Arizona
74 F250 headlight problem
Hi, I have a 74 F250 ford camper sp. Have owned it for 16 years ,I use it to haul water (live in Az no well) any way if you turn on lights and set still they work ok but as soon as you move they blink off and on (mostly off) I have replaced the wiring harness from the firewall to the tail lights and the headlight switch ,the dimmer switch ,added new ground wires for the switch and also at the headlights , have been running this for a month with out the dash in to see if any thing is moveing (wire harness) everything seems ok there , the harness going to the headlights seems to be good have unrapped it and inspected each wire all ok , don't know where to go next, any advice ? thank you Slim
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Joined: Jun 2004
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From: indiana
Headlight relay
Slimone,
Your problem is probably the "headlight relay". Early ford trucks (mid 60's to Late 80's) used a high amp relay to operate the headlights. When thes things get old and tired they will kick off and on. Initially when the problem starts the relay will "flicker" off and off rapidly trying to "clean" the contacts. As the relay gets older, the heating problem internally will cause it to stay off for long periods of time.
This relay is a small retangle metal box (about 1 1/2"- 2" by 3/4"- 1" with a mounting plate and three wire pigtail about 4" long. They were usually in the drivers fender well area close to the cab. Ford was still carrying this part as a couple of years ago and will cost you betwee $50.00 and $75.00. If the parts guy is good or has been there awhile, he will know exactly what you need as these things went bad on a regular basis.
Smitty88
88 diesel, 92 flareside, and 04 superduty
Your problem is probably the "headlight relay". Early ford trucks (mid 60's to Late 80's) used a high amp relay to operate the headlights. When thes things get old and tired they will kick off and on. Initially when the problem starts the relay will "flicker" off and off rapidly trying to "clean" the contacts. As the relay gets older, the heating problem internally will cause it to stay off for long periods of time.
This relay is a small retangle metal box (about 1 1/2"- 2" by 3/4"- 1" with a mounting plate and three wire pigtail about 4" long. They were usually in the drivers fender well area close to the cab. Ford was still carrying this part as a couple of years ago and will cost you betwee $50.00 and $75.00. If the parts guy is good or has been there awhile, he will know exactly what you need as these things went bad on a regular basis.
Smitty88
88 diesel, 92 flareside, and 04 superduty
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Sorry but, I have quash that reply.
Actually it is GM vehicles that use a relay system.
Ford vehicles have a circuit breaker as part of the switch. This is what causes Flickering lights.
The FIX is to intall a Relay system into the headlight circuit.
Go to the tech article & look for Whiter Whiters & Brighter Brights.
https://www.ford-trucks.com/article/...r_Brights.html
Another thing you can do is to clean up & protect the charging system circuitry by checking ALL grounding spots, Battery cables, Starter relay, Voltage regulator to make sure all connections are corrosion free then applying di-electric grease for corrosion proofing.
Actually it is GM vehicles that use a relay system.
Ford vehicles have a circuit breaker as part of the switch. This is what causes Flickering lights.
The FIX is to intall a Relay system into the headlight circuit.
Go to the tech article & look for Whiter Whiters & Brighter Brights.
https://www.ford-trucks.com/article/...r_Brights.html
Another thing you can do is to clean up & protect the charging system circuitry by checking ALL grounding spots, Battery cables, Starter relay, Voltage regulator to make sure all connections are corrosion free then applying di-electric grease for corrosion proofing.
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From: Dolan Springs Arizona
Hi Smitty, Thanks but I should be so lucky , the only relay under the hood of mine is a horn relay that has been unhooked for years , sorry could it be under the dash ? will pull the speed o cluster back out and see as soon as this liquid sun shine stops lol . thanks anyway ,will get back on this to you . thanks again Slim
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I went through all the same problems and replaced all of the switches and then added the relays and new wiring with new bulb connectors as per the "brighter lights" link on the forum and finally lights that are bright and always work.............btw the instructions in the link will work without the beer, if that is an issue
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From: Dolan Springs Arizona
Hi, Yes the times I have tried it the lights will stay on setting still, agree there is no relay, the last time I replaced the head light switch the one I took out was burnt bad at the plug . Cleaned it good and put in a new switch and also add a new ground at the switch (old one was a small18ga running to inside of dash) replaced it with a 14ga to the firewall, Have checked for shorts all over the truck with no luck have replaced all grounds ,body, lights, motor to body , replaced alt ,all tho the old one was chargeing good ,so far nothing has helped, checked out site for changeing wiring with relays ,thats next, thanks Slim