Gentlemen,

I know, I know - bad connection to hunt down. But before I spend hours doing that fun job, I was wondering if there is anything else that it might be that can be checked directly.

The problem is that various lighting systems are turning on and off randomly as I drive. I hit a bump, the headlights go out. Ten seconds later, they come back on. Then the gas guage isn't working. Then the dash goes dark. Then a few miles later it all comes back on. Then the headlights go out again for a few seconds.

I've wiggled and jiggled every connector and every wire under the hood, unable to reproduce the effect.

I've replaced the main light switch in the dash, and the high/low beam floor switch.

Sometimes it take a long time for the headlights to come back on. In those times, if I leave the light switch on, I can hear a pinging sound in the switch. "Click, ping......click, ping.....", like the dull twang of someone plucking a spring. There's module under the hood beside the solenoid that makes that same noise in unison. But then I drive it over some more bumps and it all comes back on.

Other than tracing wires and lookinf for bad connections - any ideas?

Thanks.

 

is the block well grounded to the frame? Sounds like a bad ground to me. There is a circuit breaker on the light switch but if you already replaced it that shouldn't be the problem.

 

Fred, here's two places to start: First check the connection on the starter relay/solenoid that the power wires attach to. Next look at the negative battery cable connection where it connects to the engine block. The gauge lights are incidental to the headlight circuit, so the problem is between the switch and the solenoid connection.

 

Mine does something like that too! I'm dreading the wire hunt down! Sometimes they all work...sometimes they don't. I never loose headlights or radio though..*scratching head*...I have no idea why...dash, tail lights and side lights all go buh-bye all of a sudden...5-10min they all come back.

Cool trick of the week: honk my horn - lights go out! *L*...it is true!
Crazy old machine...

 

My 73 acted very similar. After replacing the headlight switch and dimmer switch, I finally stumbled on the cause - shorted wiring. Near the rear bumper the taillight wires go through a hole in the crossmember. There should be a rubber grommet there, but mine was long gone and the wires had rubbed against the frame shorting them out. That's why it was affected by bumps. So I repaired the wires and covered them with some heater hose where they pass through the frame. No more light problems for several years now... It's worth checking into on your pickup.

Marty

 

the noise your hearing in the headlighyt switch it the circuit breaker, if it's coming on and off quickly it has a short in a headlight wire somewhere. I don't think the park lights go the the CB just the headlights.

 

The only thing no one mentioned it to remove the voltage regulator and clean off the back of it where it grounds to the inner fender.
The apply some di-electric grease to prevent corrosion of the new ground you have made.

You never mentioned the radio going out intermittently but maybe it does too.


You mentioned the guel gauge...how about the Temp gauge...what did it do ?..the same thing ?

You may need to remove the cluster and clean it and the plug connector ,to remove any corrosion.

 

When your headlight are on, reach under the dash and touch the head light switch, if the head light switch is getting hot (really hot) then the headlight switch is defective and will need replacing.

 

I agree with thelonerangerxlt, Check the connection and wires at the fusible link located at the starter soleniod (relay) by the battery. the fusible links and connections are mounted to the relay and and is where the positive battery cable end attaches. Check the connections, and follow the fusible link from the relay down towards the solder connection going to the alternator. Then follow the wires from around the solder connection toward the rear fire wall of the cab, and check for a bad wire or connection. These fusible links is what powers the ignition switch and headlights and horn.

 

Seperate issues maybe? It sounds like loose contacts in the headlight switch, The gas gauge is a common problem on these models. When the loose contacts move then it kicks the relay on and off.
just a thought

 

When there is trouble with a fusible link you don't have power because it melted doing its job.

This is more of an intermittent problem that involves connections or grounds.
My guess it a bad ground in the electrical supply (circuit) line.

 

Lotta good thoughts ya'll...I appreciate them! 1975Ford: Thanks for the trail! I'm going to check that this weekend.

 

I have the same problem with the lights going on and off my switch does get hot and makes the noises. I have tried two new headlight switches a new voltage regulator and cleaned every connection I can find. I still can't fix it I think that to much power is going to the headlight switch and burning them out because they work for about 8 seconds and then start going on and off. What do you guys think.

 

Are you replacing them with NEW, or Used switches? and what are you running for headlights.

 

New switches and stock headlights. I found the problem everything was getting grounded by the rear license plate light. I wiggled it and all my lights came on I cut the wire and everything works. My brake lights even work now but that may have been from me putting in the new switches. I wasn't very happy about it but at least it's fixed.