In the 'dark'
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5th Wheeling
Joined: Mar 2015
Posts: 47
Likes: 3
In the 'dark'
1971 F-350 cab & Chassis. New voltage regulator, new headlight switch. Did both of those a year and a half ago. Haven't driven the truck much in the dark since then and when I have driven in the dark I have had no issues until Friday night. Coming home from a cruise night while on a dark back road I had my high beams on and all of a sudden the lights go out. Nothing. Darkness. Came back on in a second or two and blinked a few more times. Went back to low beams and a half mile later they went out too. About three more flickers and it was good until I got home. About four more miles. Once in the driveway they went out completely again. I did have my high beams on when I pulled in the driveway.
Any ideas? Happen to anyone else? Everything else in the truck is fine and no issues with the engine running or other light working. Nothing going dim either.
Any help would be appreciated. Don't want to drive the truck at all now since I leave for work in the dark.
Any ideas? Happen to anyone else? Everything else in the truck is fine and no issues with the engine running or other light working. Nothing going dim either.
Any help would be appreciated. Don't want to drive the truck at all now since I leave for work in the dark.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 784
From: Simi Valley, CA
1971 F-350 cab & Chassis. New voltage regulator, new headlight switch. Did both of those a year and a half ago. Haven't driven the truck much in the dark since then and when I have driven in the dark I have had no issues until Friday night. Coming home from a cruise night while on a dark back road I had my high beams on and all of a sudden the lights go out. Nothing. Darkness. Came back on in a second or two and blinked a few more times. Went back to low beams and a half mile later they went out too. About three more flickers and it was good until I got home. About four more miles. Once in the driveway they went out completely again. I did have my high beams on when I pulled in the driveway.
Any ideas?
Any ideas?
Driving along with low beams, step on the switch to change to high beams, the headlights go out. Same thing occurs if switching from high to low beams.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
This is a classic problem with older cars and trucks, the headlight wiring takes a long circuitous route. Excessive resistance at the engine ground point, cables and connections to engine, frame and cowl means there is quite the voltage drop. The switch heats up because of the current, the integral circuit breaker starts to trip. Fuses are never used in headlight circuits for this reason.
These old trucks always need some dedicated time working on cleaning up ground paths and connections. Usually the big multi-pin wiring harness connectors through the firewall are corroded up pretty badly too. Automotive OEM always use the shortest lightest thinnest cables they think they can get away with, it all sort of works when new but quickly starts to fail after a few years. You're at 50, surprised they work at all. Get some nice fat cables from your local tractor supply and replace the battery and starter cables, to frame and solenoid &c, and to the cowl.
These old trucks always need some dedicated time working on cleaning up ground paths and connections. Usually the big multi-pin wiring harness connectors through the firewall are corroded up pretty badly too. Automotive OEM always use the shortest lightest thinnest cables they think they can get away with, it all sort of works when new but quickly starts to fail after a few years. You're at 50, surprised they work at all. Get some nice fat cables from your local tractor supply and replace the battery and starter cables, to frame and solenoid &c, and to the cowl.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
3x the dimmer switch been there done that on a dark 35 mile road..
Also have had the head light plug harness where in plug together near by the hood hinge. My was all green with corrosion, cleaned with a brass brush and
put some electrical grease on it back in 1983 but not driven at night much any more since sold c/o camper.
Orich
Also have had the head light plug harness where in plug together near by the hood hinge. My was all green with corrosion, cleaned with a brass brush and
put some electrical grease on it back in 1983 but not driven at night much any more since sold c/o camper.
Orich
FTE Legend
Joined: Nov 2015
Posts: 30,876
Likes: 4,115
From: Angier, NC
This is a classic problem with older cars and trucks, the headlight wiring takes a long circuitous route. Excessive resistance at the engine ground point, cables and connections to engine, frame and cowl means there is quite the voltage drop. The switch heats up because of the current, the integral circuit breaker starts to trip. Fuses are never used in headlight circuits for this reason.
These old trucks always need some dedicated time working on cleaning up ground paths and connections. Usually the big multi-pin wiring harness connectors through the firewall are corroded up pretty badly too. Automotive OEM always use the shortest lightest thinnest cables they think they can get away with, it all sort of works when new but quickly starts to fail after a few years. You're at 50, surprised they work at all. Get some nice fat cables from your local tractor supply and replace the battery and starter cables, to frame and solenoid &c, and to the cowl.
These old trucks always need some dedicated time working on cleaning up ground paths and connections. Usually the big multi-pin wiring harness connectors through the firewall are corroded up pretty badly too. Automotive OEM always use the shortest lightest thinnest cables they think they can get away with, it all sort of works when new but quickly starts to fail after a few years. You're at 50, surprised they work at all. Get some nice fat cables from your local tractor supply and replace the battery and starter cables, to frame and solenoid &c, and to the cowl.
A dimmer either works or does not, never have I seen one that was working not touch anything and the lights go out.
As said the breaker in the switch heats up, breaker trips and lights out.
Once it cools it resets and the lights come back on.
This will happen faster with the high beams on as they pull more juice thru the head light switch.
Same if you have a trailer hooked up as the trailer light add more load to the switch.
It is a 3 part fix.
As Tedster said check & clean grounds and connections.
Replace through head light switch. The breaker tripping makes it weak and will trip faster each time.
Add relays to the head lights. This will take some of the load off the switch. The switch is now used to switch the relays so litte power for this.
And the plus side you get brighter head lights as they noe get a full 12 volts from the battery.
LMC sells a kit to do this, no cutting of the trucks hsrness, but can find it on Amazon also.
Dave - - - -
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
Even with a new headlight switch, if you run newer halogen sealed beams they draw too much current(especially on brights) and will pop the circuit breaker built into the headlight switch. The only good way to eliminate that is to install relays for each headlight. Like mentioned, it removes the heavy current draw on the headlight switch. This is the same basic set up they run in newer cars.
Yes, the bright switch can give you headaches it if sticks on or off. If yours is crusty or stiff, might as well replace it also. It was a very common problem, thus they started using the t/s stalk to control the brights.
Yes, the bright switch can give you headaches it if sticks on or off. If yours is crusty or stiff, might as well replace it also. It was a very common problem, thus they started using the t/s stalk to control the brights.
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Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Where folks run into trouble is thinking that installing halogens will improve headlight brightness.The problem, the underlying fault is the excessive voltage drop due to corrosion and overage, undersized cables. Any bulb type brightness falls off a cliff if the voltage drops at the terminals even slightly. Simply installing halogens alone may make the problem worse.
Now it is true that headlight relays take the load off the switch. BUT, it's kind of a crutch, to a fault that should be remedied. If the headlights are dim, or switch breaker is tripping, then the basic engine wiring & grounding is in poor shape by definition. This would mean the ignition, heater blower, and other accessories are also starved for current.
The way to check is to measure the voltage drop at either the + or - headlight terminals under load, while bulb is energized. If more than just a few tenths of a volt then the grounds and connections are no good. Get everything squared away, replace those old stiff cables, clean up the connectors etc, THEN install a set of headlight relays - they will be that much brighter!
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Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
My floor high/low beam switch was all crusty from being wet & muddy for long periods of time since my truck was used 24/7 on the roads in a open pit mine at Kaiser steel
where the haul roads were kept wet for dust control. some pickup the floors did not last more then 3-4 yrs which was about the end of the usefulness for most of the pickup used at the mine site. Dodge pickup was about 3 yrs until the floor rusted through badly and Kaiser went back to Fords again.
I kind of assume that in the east where salt is used on the roads the a person who may have wet snowy boots may be using the high/low beam switch a lot could soak that floor switch
as a repeated use would corrode the wires /or contacts in long term use.
Like what happen to my floor switch. Then about four yrs later was when had trouble with the head lights once again. At this time , I replaced the head light switch which did nothing
to correct the blinking problem on high or low beam.
So went to the head light plug an checked the voltage about zip. so followed the wires back to the cab eng bay harness plug an where was my problem.
Not the light switch.
Orich
where the haul roads were kept wet for dust control. some pickup the floors did not last more then 3-4 yrs which was about the end of the usefulness for most of the pickup used at the mine site. Dodge pickup was about 3 yrs until the floor rusted through badly and Kaiser went back to Fords again.
I kind of assume that in the east where salt is used on the roads the a person who may have wet snowy boots may be using the high/low beam switch a lot could soak that floor switch
as a repeated use would corrode the wires /or contacts in long term use.
Like what happen to my floor switch. Then about four yrs later was when had trouble with the head lights once again. At this time , I replaced the head light switch which did nothing
to correct the blinking problem on high or low beam.
So went to the head light plug an checked the voltage about zip. so followed the wires back to the cab eng bay harness plug an where was my problem.
Not the light switch.
Orich
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
No, they won't. Not if the grounds and wiring is cleaned up. I've been running halogen sealed beam headlights in my 30 amp generator equipped truck for years and years. If you actually pencil out the increased current draw with halogen versus tungsten bulbs it is not excessive in any way and well within spec and overhead.
Where folks run into trouble is thinking that installing halogens will improve headlight brightness.The problem, the underlying fault is the excessive voltage drop due to corrosion and overage, undersized cables. Any bulb type brightness falls off a cliff if the voltage drops at the terminals even slightly. Simply installing halogens alone may make the problem worse.
Now it is true that headlight relays take the load off the switch. BUT, it's kind of a crutch, to a fault that should be remedied. If the headlights are dim, or switch breaker is tripping, then the basic engine wiring & grounding is in poor shape by definition. This would mean the ignition, heater blower, and other accessories are also starved for current.
The way to check is to measure the voltage drop at either the + or - headlight terminals under load, while bulb is energized. If more than just a few tenths of a volt then the grounds and connections are no good. Get everything squared away, replace those old stiff cables, clean up the connectors etc, THEN install a set of headlight relays - they will be that much brighter!
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
I'm not saying I disagree with Ted. But 4X dimmer switch. What Ted said to do is worth doing. Hands down. But I think the immediate problem is the dimmer switch. I HAVE had the headlights go out on me. Only guys, I was driving around a snowy Colorado Mountain road in a 1972 Chrysler station wagon. No guard rails. Full of people. All of a sudden low beams went out. Stabbed the dimmer switch and had high beams. Changing the dimmer switch solved the problem once back in Arizona.
Cargo Master
Joined: Feb 2006
Posts: 3,008
Likes: 250
From: North Pole, Alaska
I'm not saying I disagree with Ted. But 4X dimmer switch. What Ted said to do is worth doing. Hands down. But I think the immediate problem is the dimmer switch. I HAVE had the headlights go out on me. Only guys, I was driving around a snowy Colorado Mountain road in a 1972 Chrysler station wagon. No guard rails. Full of people. All of a sudden low beams went out. Stabbed the dimmer switch and had high beams. Changing the dimmer switch solved the problem once back in Arizona.
New User
Joined: Oct 2018
Posts: 3
Likes: 1
Glad to hear y'all bashing this one out! My '67 stepside has started doing the same thing! My wife and I were going for a little evening stroll in ol' Rosie when all went dark...county lane, blind curve, steep ditches...she screamed and I started stomping the dimmer like I was doing an Irish jig. Not fun, but at least now I have some confidence that I can stop thinking about a new wiring harness.
Drew
Drew
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5th Wheeling
Joined: Mar 2015
Posts: 47
Likes: 3
Well it's been a while and I had to look up my own post -- I had this problem again the other night. Last year I replaced the dimmer switch and all was good. Again not much night driving though. Friday night I was on and off the new dimmer and the lights went out as I pulled in the driveway. Only a 4 mile run. Going to follow the wires around and look for bad, crusty, corroded connections etc and also get a relay kit.
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