I'm looking for a few suggestions to solve this issue.

1988 Ford F250

I have an intermittent issue that I can't seem to pin down. Occassionally when I pull the headlight switch out to turn the truck lights on the starter energizes.

It doesn't matter if the ignition key is on or off or even in the ignition.

I tried to follow various wires from the switch to see if the previous owner somehow tapped in to them, but have not found anything.

The hardest issue is that it is intermittent so trying to track down the problem is baffeling me...

Suggestions!!!

Thanks

 

The easiest circuit to trace will be the start circuit. It leaves the ignition switch on a red/blue wire(the ignition switch is on top of the column, under the dash). From there it goes to a clutch switch if you have a manual, or goes through the firewall and down to the side of the tranny if you have an automatic.

It goes through the clutch switch or the park/neutral safety switch, and is still red/blue when it leaves, and goes up to the starter solenoid on the passenger side fender.

I would follow this along as much as possible, looking for any damaged or melted wires. Usually they get damaged underneath the truck near the exhaust, and sometimes it will mysteriously start cranking when the back-up light wire and the red/blue wire get together. But that has nothing to do with the headlights, so I would look under the dash. and at the firewall plug where these two circuits are close together.

 

Thanks for the info...I will trace that wire tomorrow....

with further diagnosis on the headlight switch I was able to determine that by disconnecting the center brown lead from the switch the problem disappears...hmmm

 

The brown lead is the running lights circuit. They have their own fuse, and it comes out of the fuse box on a tan/white wire, and runs to the headlight switch. It then comes out of the headlight switch on the brown wire, and runs all over the entire truck, feeding the running/marker lights, front, side and rear.

 

Thanks Franklin2...

Since I just got the truck a couple weeks ago, I haven't had a chance to pick up a service/repair manual...but thats my next purchase...

Any suggestions on who puts out the best...Chilton...etc...

Thanks

 

If you can afford it, the factory manual is the best. Here it is;eBay Motors: 1988 FORD TRUCK F B C SERIES SHOP MANUAL SET (item 150255114296 end time Jul-03-08 22:56:28 PDT)

 

If I am going to buy one, I might as well get a good one...after all the vehicle is already a few years old..and I'm sure the book will be used more than once!

Thanks for the help...

Now ...I just have to tackle the AC

 

Here's a link to a free set of Maint Manuals plus wiring diagrams:

Bedford Public Library -- AARC User name AND password is the same: library

 

BPofMD - Thanks for that link...

Gotta love anything thats free....I'm going to have a look at that right now!