head light problem
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Senior User
Joined: Jan 2007
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From: middle of no where, MI
head light problem
I have a 86 F 150. EFI 351W. I've been havin a headlight problem. I'm assuming its the relay. I'll be drivin down the road and my headlights just shut off and turn back on and i look like an idiot at night because my headlights are just flashing on and off. So as i said before my guess is the relay because i've already replaced the switch and it still does it. I cleaned all the connections already. So my question is... Where is the headlight relay?
also. none of my dash lights come on now either (ever since the headlight problem started) so i cant see my fuel gauge or how fast im going at night.
also. none of my dash lights come on now either (ever since the headlight problem started) so i cant see my fuel gauge or how fast im going at night.
Last edited by ford_racing_4_life; Nov 11, 2007 at 10:49 AM.
Lead Driver
Joined: Dec 2002
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From: Kuna ID
I think the relay is inside the switch. Are you running aftermarket headlights that draw considerably more power than stock. They could be overheating the new switch. Several places sell a relay harness kit that pulls the light power from the battery instead of through the switch. You could also do it yourself with the instructions that I believe are in the tech article section.
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Senior User
Joined: Jan 2007
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From: middle of no where, MI
Franklin- i thought that too at first, but the dash lights and reverse lights dont work either so im thinkin its a relay.
I'm not running aftermarket lights or anything like that. It just started doin it one day. I've seen the headlight harnesses that draw the power from the battery and am considering tryin that
I'm not running aftermarket lights or anything like that. It just started doin it one day. I've seen the headlight harnesses that draw the power from the battery and am considering tryin that
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From: Virginia
If the dashlights are blinking with the headlights, then I would suspect the plug at the switch may be melted or the connectors inside the plug are loose.
The dashlights are fed from the running light circuit. Are the running lights blinking? The headlights have their own separate feed. So the only common thing they have is the headlight switch connector or the headlight switch itself.
The reverse lights are totally separate circuit too.
Find out exactly what is blinking and what is not. That will narrow down where the problem is. The circuits originate and branch off in a certain order, so if certain lights are failing, and others are not, that will be the clue we need.
The dashlights are fed from the running light circuit. Are the running lights blinking? The headlights have their own separate feed. So the only common thing they have is the headlight switch connector or the headlight switch itself.
The reverse lights are totally separate circuit too.
Find out exactly what is blinking and what is not. That will narrow down where the problem is. The circuits originate and branch off in a certain order, so if certain lights are failing, and others are not, that will be the clue we need.
Last edited by Franklin2; Nov 11, 2007 at 07:39 PM.
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Joined: Jul 2003
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From: Pittsburgh
If you've already replaced the switch and *only* the headlights are flashing, you're to the point of needing the wiring conversion that feeds staright off of the battery.
Stock, headlights are fed off of the battery, to the switch, and then out to the headlights using 18ga wire. It's about a 15-20' journey for the electricity through entirely too small of wiring.
After 21 years of god knows what, the wires have corroded at the connectors, but also inside the insulation itself. The resistance is just too great for the draw the headlights need and it trips the circuit breaker (which is inside the headlight switch), and shuts the lights off.
That's the "click" you should be hearing when the lights shut off and then when they come back on.
Only ways around this are a fresh wiring harness or the conversion harness.
Justin
Stock, headlights are fed off of the battery, to the switch, and then out to the headlights using 18ga wire. It's about a 15-20' journey for the electricity through entirely too small of wiring.
After 21 years of god knows what, the wires have corroded at the connectors, but also inside the insulation itself. The resistance is just too great for the draw the headlights need and it trips the circuit breaker (which is inside the headlight switch), and shuts the lights off.
That's the "click" you should be hearing when the lights shut off and then when they come back on.
Only ways around this are a fresh wiring harness or the conversion harness.
Justin
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From: middle of no where, MI
Thanks Hoxxi. I'm probably going to just order the conversion harness.
The dashlights are not turning on at all. The parking lights are working perfectly. So I'm assuming that the wires are bad somewhere. The interior floor lights work fine. I dont know if the dome light works or not because theres no bulb in there. So basically the headlights flash on and off and the dash lights havnt even tried to turn on since the headlight problem started. So im gunna go with hoxxi's advice and replace the wires.
The dashlights are not turning on at all. The parking lights are working perfectly. So I'm assuming that the wires are bad somewhere. The interior floor lights work fine. I dont know if the dome light works or not because theres no bulb in there. So basically the headlights flash on and off and the dash lights havnt even tried to turn on since the headlight problem started. So im gunna go with hoxxi's advice and replace the wires.
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Joined: Jul 2003
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From: Pittsburgh
Only take my advice if that's what's wrong.
If the headlights aren't coming on at all the conversion harness won't help since it uses the headlight circuit to trigger the relays.
And your dashlights not working are a seperate issue from what causes the headlights to flash.
Again, if it's the wires having too much internal resistance you'll hear a "CLICK" when the lights go out and when they come back on. You might not be able to hear it while driving, but try parking your truck, turn on the highbeams, and wait.
Justin
If the headlights aren't coming on at all the conversion harness won't help since it uses the headlight circuit to trigger the relays.
And your dashlights not working are a seperate issue from what causes the headlights to flash.
Again, if it's the wires having too much internal resistance you'll hear a "CLICK" when the lights go out and when they come back on. You might not be able to hear it while driving, but try parking your truck, turn on the highbeams, and wait.
Justin
