Flickering High Beams

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Feb 19, 2007 | 07:59 PM

eman resu

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Flickering High Beams

I have an '85 F-150 with a flickering headlight problems. Everything is fine when the low beams are on, but when I turn on the high beams, they flicker rapidly. I've already checked the dimmer switch and it's fine. What's weird is that when I disconnect one of the headlights (either one), the other works fine...even on high beam. This seems to indicate the problem is when there is too much power needed to light both high beams. What could be causing this? Where should I look and how can I diagnose this problem? Thanks for the help.

Feb 19, 2007 | 08:17 PM

butch h

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Might be a weak headlight relay.

Feb 19, 2007 | 08:41 PM

eman resu

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I could be wrong, but I don't think this truck has headlight relays. At least I don't see them in the wiring schematic.

Feb 19, 2007 | 08:58 PM

Franklin2

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From: Virginia

The headlight switch has a circuit breaker built into it. Ford has had lots of problems with their headlight switches and plugs. The plug gets loose and gets hot. This melts the plastic on the plug and makes things worse.

I would pull the headlight switch out and see what it looks like. If it looks ok, possibly a new headlight switch will fix it. If it's really melted, I think you can get a new pigtail with a new plug to repair the old harness. I would get a new switch either way you go.

Feb 20, 2007 | 06:28 PM

patho44

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From: Prairie Village, KS

voltage regulator..... at least the old mechanical ones when going bad would cause fliker as the switch open and closed rapidley

Feb 20, 2007 | 08:27 PM

Holmesuser01

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From: Asheville, NC

Check out your high beam switch on the floor. They do corrode out over time.

Feb 20, 2007 | 08:56 PM

Mil1ion

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The problem is the circuit breaker in the headlight switch,

It's a common problem in Ford because of this circuitry.

do the Relay upgrade and improve your lighting by making it more efficient and eliminating the inner switch C/B

https://www.ford-trucks.com/article/...r_Brights.html