First off, nice ride.  Always did like the Fairlanes, almost bought one more years ago than I care to admit. 

Second, your idea that it seems like a circuit breaker is triping is likely on the right track.  If its like a Mustang, and it wouldn't surprise me if it is, there is a circuit breaker built into the headlight switch.  What's likely happening is that the draw from modern headlight bulbs is overloading the circuit and causing it to trip out.  Once the load's off, and it cools down, the breaker resets and it works again.  This was happening on my Mustang, except I would lose my headlights.  A bit scary.  The solution is to install relays that can move the high load power switching from the headlight switch to the relay.  I bought a kit to do mine, but honestly, now that I see how it works I could have saved a lot and just sourced the stuff myself.  Installation is pretty easy, I used the headlight pigtails to splice in the connections, keeping my expensive main harness clean.  Carefully mounting the relays and routing the wiring I think it looks like it belongs there other than the relays don't look like something from the '60s, but if I'd wanted to hide them I could have, instead I mounted them to the LH inner fender near the front of the car (you want them as close to the lights as possible).  You need two relays and some wire.  The power wire, which is going to tie to the battery, or probably most easily to the battery side of the starter solenoid, should be 10 gage wire.  The wires feeding power to the headlights should be 10-12 gauge too.  The trigger wires can be lighter 14-16 gauge stuff.

I really don't think it is a head light issue, although the relay upgrade is a good idea. If the head lights were causing the problem you would lose them too. The 66 Mustang has a circuit breaker in the headlight switch to control the lights. I think, oh no hear goes my wonderful memory again, the 68 has 2 circuit breakers in the headlight switch. This is why the headlights are staying on. Sounds like it’s a ground problem or a bad headlight switch. If there is a plug for the wires going up the steering column, you could try unplugging it. This would tell if it’s a horn problem as GP suggested. You don't have to drive it, just turn the lights on for 20 minutes or so. Maybe when I get home and check some wiring diagrams I'll have some more ideas. Using my memory just might get you into trouble.
 

If the headlights are still working when all the others fail, then the headlight breaker is not the issue.  All the other lights run off of fused circuits, so I would suspect something at the fuse box.  It could be a fuse that lets loose when it gets hot or a corroded fuse clamp.  My first step would be to replace turn signal and taillight fuses.
Always try the cheapest and easiest fix first.  If that is not the issue, at least you know you have good connections there as you troubleshoot the rest of the wiring.

phil wrote:

MustangSteve wrote:

If the headlights are still working when all the others fail, then the headlight breaker is not the issue.  All the other lights run off of fused circuits, so I would suspect something at the fuse box.  It could be a fuse that lets loose when it gets hot or a corroded fuse clamp.  My first step would be to replace turn signal and taillight fuses.
Always try the cheapest and easiest fix first.  If that is not the issue, at least you know you have good connections there as you troubleshoot the rest of the wiring.

 
Thanks guys and to you MS. I ordered a Motorcraft replacement switch just because I could probably stand to replace everything on the car LOL

The fuses and the panel all appeared to be in good shape but I will start looking them over more carefully. I originally suspected a bad ground but I think I found all the ground spots and they are all clean and on good metal (there may be a few I do not know about thought)

This car had no turn signals until very recently when I found a 68 Ranchero in the junkyard and grabbed its switch. This issue popped up before that though.

I'll see what the new switch does for me and then I'll look at the other stuff mentioned in this thread.


I kinda stepped away from the car thing for a while but a 99 Jeep Cherokee has me back wrenching. I sold my 70 Fairlane to pay for some of my grad school tuition. I miss that car quite a bit

I REMEMBER YOU, NOW!!!!  You're the guy that took all the pictures with really cool background...Old plants etc. Welcome back.............missed the pics!
 

Just want to reiterate one point. The switch could be bad but would be my last guess. When I said a bad ground, I didn’t mean a loose or bad connecting ground, which causes a lot of problems. I meant a bare wire shorting to ground. That is why I suggested unplugging the wire to the steering column. If there is a short in there things could be fine. When you turn the wheel it may cause a wire to rub to ground. I did look at my 68 Mustang prints last night and they do show 2 circuit breakers in the light switch. Really didn’t have a lot of time to dig into this much, so right now it is just a guess.
 

6sally6 wrote:

phil wrote:

MustangSteve wrote:

If the headlights are still working when all the others fail, then the headlight breaker is not the issue.  All the other lights run off of fused circuits, so I would suspect something at the fuse box.  It could be a fuse that lets loose when it gets hot or a corroded fuse clamp.  My first step would be to replace turn signal and taillight fuses.
Always try the cheapest and easiest fix first.  If that is not the issue, at least you know you have good connections there as you troubleshoot the rest of the wiring.

 
Thanks guys and to you MS. I ordered a Motorcraft replacement switch just because I could probably stand to replace everything on the car LOL

The fuses and the panel all appeared to be in good shape but I will start looking them over more carefully. I originally suspected a bad ground but I think I found all the ground spots and they are all clean and on good metal (there may be a few I do not know about thought)

This car had no turn signals until very recently when I found a 68 Ranchero in the junkyard and grabbed its switch. This issue popped up before that though.

I'll see what the new switch does for me and then I'll look at the other stuff mentioned in this thread.


I kinda stepped away from the car thing for a while but a 99 Jeep Cherokee has me back wrenching. I sold my 70 Fairlane to pay for some of my grad school tuition. I miss that car quite a bit

I REMEMBER YOU, NOW!!!!  You're the guy that took all the pictures with really cool background...Old plants etc. Welcome back.............missed the pics!
 

  Me Too!  Love that Car!
 

I should have finished my thought there.  What I was saying is that the switch wasn't my problem.  The problem was the load imposed by the new style headlights (nothing special, but modern bulbs draw a lot more than the ones they had in the '60s) was causing the switch to overheat and trip the breaker.  Converting to relay activation for the headlights is what solved the issue. 

Phil - sorry this is a little late, Mutang Monthly did a "How-To" troubleshoot headlight switches article in the June 2010 issue, link below.
I believe the switch body is the same for all Ford models for many years, the difference being the switch bracket is specific to a model.
http://www.mustangandfords.com/how-to/interior-electrical/mump-1006-ford-mustang-troubleshooting-headlight-switches/