Hi all,

I have a 1997 F-350 crew that I use for work. I travel all over and have a problem that I need to fix by Monday. Can you help?

We will be driving along and the headlights and dash lights will just go on and off. It happens so fast and is so disconcerting that I haven't been able to tell if the other lights are affected. The lights have always come back on before stopping.

There seems to be no correlation between going over bumps, whether the brights are on or off or anything else I can figure out. It will happen a few times in real quick succession and then not happen at all for 50 miles.

It has happened when I am pulling a trailer, but I am uncertain if there is a correlation. I also have a 1997 spare vehicle that I can swap/test parts if need be. I really don't know where to start and am pretty much a novice with electrics. I do have a multimeter.

Any help on where to start and what I should be looking for?

Thanks,
Jason

 

I cant be of much help but it is probaly a ground. Do you have a Hanes or Chilton manual? Find a wiring diagram and check the ground for the dash lights.

 

Here is TJ's website with all of the wiring diagrams Wiring Diagrams pictures from friends & fun photos on webshots hope that helps

 

Since it is so intermittent it is going to be tough to find. I would start by turning lights ON and while someone is watching wiggle the wiring harnesses in the engine bay and under dash. I'm assuming the rig keeps running, just the lights come and go?

 

Thanks for the wiring diagrams, but I can't read them on my computer - maybe my monitor isn't good enough. I do have the Chilton's manual, but I can't find the instrument cluster in them. I can find the headlights. I have checked the grounds by the headlights - they look good.

Could this possibly be the headlight switch? It is difficult to troubleshoot becaust it is intermittant.

The truck seems to run fine when the lights go out...

I appreciate the input

 

I have been having the same problem.....but it is just my headlights(luckally I have my driving lights wired with my parking lights so I can still see when it happens)I narrowed it down to the switch...and have a new switch sitting here that I am putting in tomorrow.I have heard that the switches are pretty common to go bad

 

I really appreciate all the replies.

I just spent some time jiggling wires, etc, and couldn't find anything that would make the headlights go out. Couldn't find any loose grounds either or wires becoming bare.

So, I wanted to practice getting into the headlight switch, so I went to my spare F250 and took everything apart - pretty simple.

Then I went over to the F350 that has been giving me problems and took it all apart. Everything is the same except that the plastic piece that mates the wires (excuse the terminology) to the headlight switch is somewhat browned on one side, like there has been too much heat in there. The actual terminals themselves appear pretty clean. Is this a sign of something?

A couple of questions:
- Is there a way to test the headlight switch?
- Does the fact that my dash lights go out when the headlights do make the headlight switch more or less likely the culprit?

I am tempted to just put in the switch that I know works and try it out, but this problem is so intermittant that it wouldn't really tell me anthing if it worked for 20 miles. It is also such a dangerous thing that I would like to be as sure as I can be that I have fixed the problem.

Thanks for your help,
Jason

 

My bet its the switch......put the spare in and drive with the lights on during the day to test

 

How would I tell if the lights weren't working?

 

Is the "plastic piece that mates the wires (connector) the same on both switches? The burn marks make be think it's the switch. If you problems don't return you solved the mystery.

All you can do is Ohm out the headlamp switch, you can't really test the switch for intermittent problems. It needs to be broken for the test to reveal anything.

You dash lights are controlled by that switch too.

 

I figured you would notice the dash lights if they went out......or set up a test light and lay it on your dash

 

The plastic piece is the same for both trucks - the one with the problem has the burn marks.

The test light is a good idea - I doubt I would notice the dash light in the daytime.

Thanks for the input,
Jason

 

Or go to radio shack and see if the have a cheap 12 volt buzzer you can wire into the headlights and leave it under the hood for a while.

 

I really like the buzzer idea.

Would such a buzzer go off when the circuit is broken? Which wire would be the best to tie into and what would be the best way to tie in?

I am pretty much a novice when it comes to electricity...

 

The test light might be a better idea for you then......all you will need to do is ground one end and the other to the back of the switch....just make sure your test light comes on when you switch on the lights....there is a constant hot that is there that wont help you if you tie into it