Headlight issue

[84FS460]

My 84 F250s headlights flicker on and off after driving for about 10 or 15 minutes but only does it while driving and not while at a stop. My dash and marker lights work fine so it made me think it was the dimmer switch which I replaced turns out didn't fix it. I don't think its a bad ground because there are two separate grounds for each headlight and they flicker at the exact same time, but I might be wrong. I don't have any additional lights on the circuit and I installed aftermarket lights that convert from H6054 bulbs to 9003 bulbs. Would it be at the headlight switch?

[Gary Lewis]

I doubt it is the headlight switch since it does it when you are moving and not sitting still.  But it is possible it is the switch.  However, I suspect a bad connection in the wiring that wiggles while you drive.

Do both the low and high beams do it?  If so then it is something common to them, and as shown below, that includes the black/orange wire coming to the switch, the switch itself, and the red/yellow wire to the dimmer switch.  I'd turn the lights on and lay down under the steering wheel and gently move those wires and see what happens.

Typically what happens is that a connection gets bad and that causes heat.  And if you went with higher wattage lights that makes the connections heat up faster.  So see if they get hot.

If you find that is the problem then you need a headlight relay kit to take the load off the switch and the wires to it.

[grumpin]

I have had headlight switches go bad, but they didn’t flicker. Dead off until they cooled, on, then off again.

[ArdWrknTrk]

I've seen the same thing Dane has, but I always thought it was some kind of circuit breaker in the switch.

If only the headlamp bulbs are flickering then I would look at power out of the switch and the connector for the dimmer.

[grumpin]

ArdWrknTrk wrote

I've seen the same thing Dane has, but I always thought it was some kind of circuit breaker in the switch.

If only the headlamp bulbs are flickering then I would look at power out of the switch and the connector for the dimmer.

Good idea. I remember now having a dimmer switch go bad and the lights would flicker or go off, I’d kick it with my foot till I got it replaced.

[ArdWrknTrk]

I imagine the easiest way to tell would be to back probe the wire from switch to dimmer with a test light and take it for a drive on a bumpy road.
If the light's not flashing it must be the dimmer.
But they're cheap enough to throw parts at, I guess.

[Littlebeefy]

Do you have an aftermarket heavy duty lighting harness installed? If so, that could be your issue since it would power your headlights independently of the other lighting.

[84FS460]

I found the problem and the headlights are working great it was the headlight switch. The contacts were simply bad. I am curious to see what it looks like on the inside of switch. I'll probably cut it open.

[Gary Lewis]

Yup!  You found the smoking gun, for sure.  But you should still consider installing a headlight relay.  The headlight switch and wires were marginal when new, and if you put a stronger bulb in.....

Anyway, congrats!

[grumpin]

Good find!