Hello

I have the following 1985 f-250 w/ 300 six, four speed i have had it for 9 yrs. recently I have been getting it road worthy again and upon checking the lights I noticed the following.

High beams don't work, taillights don't work, the front parking lights come on and then gradually start to blink

low beams work, turn signals work, hazards work, and brake lights work.

I have replaced the head light switch with an auto wrecker one as well as the dimmer switch on the floor.

I pulled most of the tape off of the wires in the engine bay to try to see any bare wires, but none. I could have got a junk headlight switch again I don't know.

Any insight on this issue would be greatly appreciated

Thanks

Tyrone

 

A new headlight switch would have been best, but you can do a little testing before you buy anymore parts. You need to get a voltmeter or a testlight, and then we will walk you through how to figure out what's going on.

Lets start with the headlight highbeam problem. You should have a red/yellow feeding the dimmer switch. Take your testlight or meter and with one lead on a good metal ground, test the red/yellow with the headlight switch all the way out. You should have 12 volts, since your low beams are working.

On the dimmer switch there should be two other wires coming out. One is the highbeam, and one is the lowbeam. Check each wire like you did the first. One of the these wires should have 12 volts with the dimmer switch clicked once, and then the other should have 12 volts when the dimmmer switch is clicked again.

If all that checks out, then note the color of the wire that has 12 volts when in the highbeam position. Go out to the headlights and find this same color wire. Take and unplug the plug on the back of the headlight, and put one lead of the testlight on this highbeam wire, and the other lead to a good metal ground. With the headlight switch all the way out, and the dimmer switch on high, you should have voltage on this wire.

If you have voltage, but the headlight will still not burn, take the negative lead off the good metal ground, and put it on the ground in the headlight plug. If you do not get a reading with the ground in the plug, then the ground wire to the plug is bad.

 

Thanks for replying so quick

So I found my test light and I checked the three wires going into the dimmer and into the headlights, for some weird reason high and low beams now work but still no parking lights, I checked what you said with each corresponding wire for high and low beam and all was fine. The newest problem is the front parking lights will come on constantly and then over a couple of minutes will start to flash at a non consistent rate. Just to check I turned on the hazards and they worked normally while the other filament in the bulb kept flashing like it was doing. I also think that the headlight switch I got from the wrecker was junk so I resorted to the original switch.

When I originally was messing around with the wiring 2 years ago I had a problem with the front parking lights lighting up when I stepped on the brake pedal.

I think this might have something to do with the tail light harness I ended retaping. So I might try to see if anything in the tail light harness is wrong

thanks, Tyrone

 

You probably had a loose or bad connection down at the dimmer switch. That would explain that one.

When this happens, nothing else is on. The key is off. And to make them go off you have to take the battery cable loose?

 

Sorry for not explaining


when I turn on the headlights or parking lights is when they start to act funny. all of the times I have been checking I have had the ignition off and just used headlight switch. For some reason I think there might be something messed up in the taillight harness, I was going to check today but got really sidetracked, so tomorrow I will.

 

Why do you think that? The taillights start blinking erratically too? Or is it just the front lights?

And if it is just the front lights, do you notice the green turnsignal indicators in the dash glowing or blinking dimly?

 

The taillights dont blink or pulse like the front ones do, but I do notice when I tried the left or right turn indicator sometimes they will not blink, with out rapidly moving the indicator arm, the turnsignal indicators would just stay a constant green.

Well thanks for all the help Dave I appreciate the input but for now I am off to work out of town so the truck will have to sit awhile in the driveway before I can mess around with it.


Thanks again, Tyrone