I had this happen before and thought the switch was shot and that was what blew the lights out. So I replaced both switches and bought new bulbs and that fixed it for awhile. Well This morning I was driving my mom to work since her fuel line rotted off on her car and the light flickered a bit along with the dash lights and then the lights go out. I have parking lights and highbeams but no low beams. When this happened before replacing switches didnt help, but when I replaced the bulbs everthing was fine for awhile. Any ideas?

 

Usually it is a spike in the charging system that blows both bulbs at once, and only the low beams since that's what you had on at the time. Check all grounds and connections, could be a bad regulator.

 

Very true... Is your alternator internally or externally regulated. also check the insulation on your wires. You may have a short.

 

Are you sure the bulbs are blown this time? If they are not, I would suspect the dimmer switch is bad, or the connector to it is corroded.

 

Dimmer problems. I've had this exact problem myself.

 

I just replaced both of the switches about a week ago. I had the same problem before and replacing both the switch in the dash and the one on the floor didnt fix anything. Both the headlights and dash lights will flicker and then the headlights just go. I'm gonna check all the grounds and look everything over again. One thing I noticed before, was that the headlights would occasinally flash a little brighter and at first I didnt really think much of it but since Archion mentioned voltage spikes it has me wondering if it is a VR.

 

It is actually a common ford problem, especially with the early integral regualtors. The Rugulator/brush pack can be changed easily with a torx and paperclip. You dont even have to remove the alternator!! The flash and flicker is pretty much a dead giveaway.

 

I figured that was it. I was also wondering why the heck Ford mounted the alt so far down on these trucks? I remember replacing the VR on my tbird before, easy as pie. Thanks for the help, I'm gonna go get a new VR later and let yall know how it went.

 

If the dash lights are flickering with the headlights, then I would agree with the voltage regulator. If not, I would still suspect the dimmer switch. There is a post going on in here now where a guy replaced his dimmer switch, and is still having problems with it, and suspects it may be the plug that goes to the dimmer switch, since he can kick it with his foot and affect the lights.

 

The location of the alternator was not the smartest, but it made sense from an assembly line point of view. now it does make it easy to do a 3g conversion from underneath.

 

Finally got around the replacing the VR, and well it still does it. I'm thinking there's alittle more to this than what I expected. I went to move the truck earlier and noticed that no dome light came on when the door opened, right then I knew something was up. Turned the key, nothing. Stone dead. Popped the hood and wiggled the cables, still no dome light. However shaking the battery did the trick. So just needs a new battery right? No. Put a new battery in and the lights blew out yet again on the way home. The whole way to advance auto the lights would flicker but they only did it on bumps so figured it was the junk battery, but on the way back with the new battery they did it even worse and then blew out halfway home. Needless to say I was rather pissed.

Now my question is, would a bad battery cable do this? Something else I probably should have mentioned earlier was that every once in a great while the truck would just shut off. Not quit running, I mean go completely dead as in no juice what-so-ever from the battery.

Hmmmm. After typing all this I think I might have it figured out. Ok, I dont know if this effected the trucks or not, but in my old '88 T-Bird the ignition switch took a dump and would do the same thing, well apart from blowing lights out, and I know them switches like to get hot and catch fire hence the recall. Think that could be it?

And I apologize for the lengthy post.

 

The headlight circuit does not go through the ignition switch.

 

Well my issues are evolving from blowing lights to no power to ANYTHING in the truck. Whatever it is thats causing the truck to lose all power has to be effecting my lights somehow.

I dont know, I'll look more into it tomarrow, its been a long, frustrating day. I need some sleep.

 

Are the headlight bulbs actually burning out (i.e., open filaments) or they turning off and then coming back on? If the latter, then it's likely the auto-reset thermal overload circuit breaker internal to the headlight switch is kicking off either due to A. too much current being drawn by the headlights (short in wiring or wrong headlight bulbs) or B. the circuit breaker in switch has aged and does not carry as much current as originally. Make sure no additional load such as fog or running lights have been added to the headlight circuit.

 

I had a similar problem with losing all lights and power a couple of weeks ago.

After some investigation it turned out to be the power wires (yellow I think) coming off of the alternator going to the starter solenoid. There is a factory splice there with 2 or 3 wires coming off that was all corroded.

I cut the factory splice off and replaced it with a heavy duty crimp on and have not had a problem since.