One Headlight
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Tuned
Joined: Jun 2017
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One Headlight
Hey, folks - my 1978 F250 headlights were working just fine on regular brightness, but when I hit the high-beam switch on the floor, the passenger side bulb got stuck on high. Any ideas how to fix this?
Thanks!
Thanks!
Moderator & parts slinger
Joined: Feb 2007
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From: S/W Missouri, Polk county
To trouble shoot it I would swap the bulb positions and see if the issues moves positions. If it does, I bet floor dimmer switch is bad?
To just take that step out of the equation, just replace the floor dimmer switch.
To just take that step out of the equation, just replace the floor dimmer switch.
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Tuned
Joined: Jun 2017
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The dimmer is on the floor, but it doesn't make a difference. I can turn the lights on and off completely by the dash switch, but activating the dimmer doesn't change the status of either filament.
Cargo Master
Joined: Jun 2015
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Originally Posted by applebaggins
The dimmer is on the floor, but it doesn't make a difference. I can turn the lights on and off completely by the dash switch, but activating the dimmer doesn't change the status of either filament.
Least that's how I read his question.
Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
If the dimmer switch is defective, when you step on it to switch from low beams to high beams (or vice versa), the headlamps will go out.
This is a very common occurrence with this switch (C0TZ-13A024-A / Motorcraft SW-263) that was used on most 1960's/90's FoMoCo vehicles.
This is a very common occurrence with this switch (C0TZ-13A024-A / Motorcraft SW-263) that was used on most 1960's/90's FoMoCo vehicles.
Lead Driver
Joined: Jul 2017
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From: San Jose, CA
For now I'll go by the first one and ask if the driver's side goes to high beam too, or does it go out? If it does go to high, does it go back to dim when you hit the dimmer switch again?
Does turning the headlight switch off reset them to work the same, or does the passenger side stay on high now, no matter what you do?
If so, that does not sound like the floor switch since it should effect both lamps. I guess I better go out and look at mine again, but if there is only one wire out to the low beams and one wire out to the high beams, it can't be the switch effecting only one lamp.
As was asked, does the driver's side high beam come on at all? And does the dash indicator light come on?
I realize you responded to the question, but that answer was very confusing.
If the answer to those is no the driver side does not activate on high and the dash light does not come on, then it's very possible your switch has gone AWOL like the others have already said.
Paul
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Ford Parts Specialist
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From: Simi Valley, CA
I'm whizin' along on I-40 late at night in my '65 F100 between Barstow and Needles. I was headed to Seligman AZ to join a Route 66 rod run.
With little traffic coming the other way at 2AM, I'd flick the switch to high so I wouldn't run over a rabbit, tortoise or hit a jackass (the 4 legged variety), all of which were common out there.
One time when I flicked on the switch to high, the *** **** headlamps went out. I knew what the problem was...corroded switch.
So I pulled over, stopped, reached under the seat, grabbed a crescent wrench and hit the switch several times. The lights came back on...and I never had the problem again.
With little traffic coming the other way at 2AM, I'd flick the switch to high so I wouldn't run over a rabbit, tortoise or hit a jackass (the 4 legged variety), all of which were common out there.
One time when I flicked on the switch to high, the *** **** headlamps went out. I knew what the problem was...corroded switch.
So I pulled over, stopped, reached under the seat, grabbed a crescent wrench and hit the switch several times. The lights came back on...and I never had the problem again.
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Tuned
Joined: Jun 2017
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I don't recall seeing an indicator light on the dash at all.
Ouch!! Glad you're ok! That's a pants-changing moment for me.
Post Fiend
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From: Waterloo, Iowa
Ah, good ole "percussive maintenance", eh?
Ford Parts Specialist
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From: Simi Valley, CA
My apologies. When I pull the switch on the dash, the headlights turn on. The driver side is normal, but the passenger side headlight is stuck on high-beam. I hit the switch on the floor and there is no change. I push the switch on the dash and the lights turn out. Basically, the lights are perpetually stuck with driver side on regular brightness and passenger side stuck on high-beam.
I don't recall seeing an indicator light on the dash at all.
It's there, all trucks have one
I don't recall seeing an indicator light on the dash at all.
It's there, all trucks have one
Same bulb used with the gauges, front fender and rear marker lamps.
But be careful, because the original 1975/79 F100/350, 1975/80 Econoline, 1978/79 Bronco instrument cluster backs were made of a composition material that can TURN TO DUST before your very eyes!
Instrument cluster back shown as 10848 in pic. With oil/amp gauges is different than with oil/amp warnings lamps, the 10K843 printed circuit boards are also different.
Lead Driver
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From: San Jose, CA
Yeah, except now we know they're both offending. So I would start with the floor switch myself, but instead of just replacing it (which is what I used to do and probably what's needed anyway) I would jumper two wires together. First the low beams, then the high beams to see what, if anything changes.
Then I would test the headlamps themselves individually. See if power is getting there, and where it's getting and why.
With the driver's side stuck on low beam, and the passenger side stuck on high beam, and the dash indicator lamp not working, you probably have multiple issues.
Hence the need for some testing. If you follow the wires and find some breaks and splices and household wire nuts, and lots of fresh electrical tape, I'd start digging into the harness.
But some simple testing with a volt-meter will tell you what needs what.
As said, the High-Beam Indicator could be burned out. But if the floor switch is not working and switching to high position, the indicator lamp will never come on even if it's good.
Since getting into the dash is more of a pain than testing the floor switch and lamps and wires under the hood, that's where I'd start.
Paul
Then I would test the headlamps themselves individually. See if power is getting there, and where it's getting and why.
With the driver's side stuck on low beam, and the passenger side stuck on high beam, and the dash indicator lamp not working, you probably have multiple issues.
Hence the need for some testing. If you follow the wires and find some breaks and splices and household wire nuts, and lots of fresh electrical tape, I'd start digging into the harness.
But some simple testing with a volt-meter will tell you what needs what.
As said, the High-Beam Indicator could be burned out. But if the floor switch is not working and switching to high position, the indicator lamp will never come on even if it's good.
Since getting into the dash is more of a pain than testing the floor switch and lamps and wires under the hood, that's where I'd start.
Paul
