Electrical/headlights failure...can anyone help?
 

Drove the Cobra a few hundred miles a couple of weeks ago, shut it off when I got home, and the head/tail lights have not worked since. Every other light works...brake lights, turn signals, emergency flashers, just no headlights or tail lights.

Of course, the first thing I thought of was the fuse, so off I went to Reliable Auto Parts and away I came with two 20amp headlight fuses (the second a spare so that if the lights go out at night I'll be able to get back on the road)...at $16 each!! No worries, I'll be on the road.

Not!!! :eek:

About the only other thing I can figure out is that it might be the headlight switch. All the stuff on this replica seems to be Ford stuff...the door handles and latches are Ford, the hood latch is Ford, the steering column is Ford, I think the fuse box is even Ford (if you can verify that with a photo, please let me know and I'll get it posted). I figure the headlight switch must be a Ford part, too.....hopefully!

So, I have a continuity tester...sort of like a screwdriver with a very fine point on the end that pierces the wire's insulation and a handle that lights up when there is electricity sensed in the conductor. Can anyone tell me which part of the headlight circuit to check first? Does the power for the headlights go to the fuse box before it goes to the headlight switch, or is it the reverse? The dimmer switch is a two-pole toggle switch, up for high beams, down for low beams, center for no beams. It makes no difference how it is positioned.

I know that grounds are a big issue with our cars' electrical problems. I know there are ground circuits for the lights at both the front of the car and at the rear...must be good because the turn signals work both front and back. Before I tie myself into a knot and stuff myself under that dash again I'd like to know how to proceed...any help would be greatly appreciated!

Cheers, and thanks in advance for whatever you can do!

Dugly :cool:

I offer these suggestions in spite of the fact that I know absolutely nothing about how your car is wired, so take them with a big grain of salt.

First, run a jumper cable from the headlight ground to a known good ground, and test the lights. If they still don't work, it's not the ground.

Second, use your continuity tester to see if power is getting to the light switch. If it is, check that it leaving the switch when it is ON. Then follow the power until you find where it stops. This is not as easy as it sounds. ... Also be on the lookout for a relay (typically four wires connected to it). It could be the problem.

Check the circuit that activates the relay.

If it is a Ford headlight switch they have a built in heat sensitive breaker that can fail completely. I have seen them where they will flash off and back on, or completely fail. That is if not wired with a separate relay...

Pics would be helpful -- is this a Factory Five Car >?

the headlight switch might have expired.

Also, check that it does not have some type of fusable link built into the wire powering either the relay or the switch. I have seen this done a few times on various types of cars.

I will get pics up this weekend...not a FFR product....body from Cobra Auto Works in OKC, chassis/assembly by Ron Godell Racecars.

I really appreciate the help, folks....will certainly follow all your suggestions as it looks like this weekend will be dedicated to getting the issue corrected.

One more Q---will one of the contacts at the fuse panel be hot? I'm still not certain where to start...which pathway the power takes. It seems to me that it must go to the fuse panel first, and then to the headlight switch, which directs the power to either the "parking lights" or the headlights....right?

The headlight switch may well have a built in relay...there are multiple wires coming off it...didn't count when I was folded up under the dash, but will get the driver's seat out of the car and spend time back under the dash taking photos and getting things out of the way. Sure are lots of wires under that dash!!!!!

Thanks, again....please, keep the suggestions coming, folks!

Cheers!

Dugly :cool:

One other Q....can I test the 20amp fuse with my continuity tester? I do have some alligator clips I could wire up for test purposes.

Thanks!

Dugly :cool:

Turn the ignition switch to ON. Take the negative side of the test light and ground it. Touch one side of the headlight fuse, then touch the other side. If the fuse is good, you will have power to both sides. This means the problem is after the fuse box. If the fuse is bad, you will have power to only 1 side. If you have no power to either side, the problem is before the fuse.

That being said, if it has a headlight relay, you may have power to the fuse and switch, but still no headlights. You would then need to check both the relay power and the main power wire into the relay. If they all have power, then the relay is bad. If either one does not have power, then you need to start tracing things backwards to either the headlight switch if you have no relay power, or to the solenoid (I guess this is where they draw the main power for the headlights..maybe rear of alternator?) if you have no main power.

Hope this makes sense. If it does not have a relay and you have power through the fuse, it is probably the headlight switch.

I had this same thing happen on my car. Apparently at some point in time, somebody forgot to correctly ground the dashboard. I would drive down the road and certain lights would just go on off randomly including the headlights as the current was backfeeding to find a ground. Took me a long time to trace that single stupid wire that was not attached correctly and was bouncing around. The dash now has 3 ground wires and I have never had a problem since.

A picture of the headlight switch would be helpful at this point in the thread.




Bill S.

I crawled under the dash to take pics...got a few of the fuse box and as good a photo of the headlight switch as I can get with all the wires in the way. I'm trying to bring this new Photobucket program to it's knees now...wish I could just get the photos uploaded like I use to.

A funny thing happened on the way to the forum, though, guys.

Has anyone ever seen a headlight switch with a built in fuse?

As I moved the wires around to get a better view of the headlight switch, I saw what looks like a glass-bodied fuse hanging on the block that is the headlight switch...the kind that looks like a tube with a wire filament inside. Well, I can't see the wire filament, but I can see what looks like a milky colored residue on the "bottom" of the fuse...could easily be melted filament.

The headlight switch also has 4 electrical connections.

Could it be that the headlight switch has a built in relay with a built in fuse?

I'll keep trying to get the photos posted...but Photobucket can put this new program where the sun don't shine!!!!

Cheers!

Dugly :cool:

Well, I managed to lock up the Kodak Share app...now I wish I could HELP Photobucket put this where it belongs!!!

Dugly :cool:

to answer the question imbedded in the photo comments...."yes"
i have seen switches with a glass fuse and switches with a circuit breaker on the end of them. look in the cole-hersee catalog they show them as universal type lamp switches.
does it look like this?

http://www.colehersee.com/assets/pro...57211-7127.jpg
Rotary Switches & Headlamp Dimmer Switches | Push-Pull Headlamp Switches | Cole Hersee - Littelfuse

Oh, yeah...looks exactly like that :)

Looks like there's a fuse replacement in my near future.

Is that a built-in relay? Here's why I ask:

The guy who built the car at least had the good sense to install the headlight switch with the fuse on the bottom of the block....a newbie might not think about that sort access issue.

I'll keep trying with Photobucket.... :o

Cheers, and thanks!

Dugly :cool:

Has anyone had any experience with the circuit-breaker type fuses, like this one:

Rotary Switches & Headlamp Dimmer Switches | Push-Pull Headlamp Switches72102 | Cole Hersee - Littelfuse

Sure would rather not have to fish a fuse in and out of the jaws if I can help it...for in case it happens again. Are they reliable? Power capable at their rating? Space might be an issue, it's pretty tight with wires in there. I can try to move them around a bit, but they're bundled and the bundle is pretty big.

Onward!...through the fog....**)

Cheers!

Dugly :cool:

Dugly,
I haven't used a switch exactly like the one you show, but all my switches are combination circuit breaker / toggle switches. I have no fuses in my car. As long as it is sized right, it ought to be as good or better than a fuse protected switch.

So far you haven't mentioned what might have caused the fuse to blow. Keep in mind that there may be more to this job than just replacing a blown fuse.

Thanks for the info on the circuit breaker type.

Yes, I have thought about what caused the overload. So far I cannot identify when and/or how the fuse failed, there was no time when I had the lights on that they failed. It's a mystery to me. The last time I drove the car at night the lights worked fine. The next time I tried to turn them on they wouldn't work....hence, this dilema. I am confident I can get the fuse and/or the entire headlight switch replaced, but as for chasing down the cause for the fuse blowing I think I'll take it to the shop that rebuilt my alternator...they did such a great job on that and I have no doubt they will do an equally good job of chasing down the problem.

Of all the problems we have with these cars....electrical always seems to be the most daunting :o

At least I have a starting point...I think I can get up in there with a dental pick and pry the old fuse out witout breaking the glass tube. Getting the new one in may be a part-time career....we'll see, I guess. I have an electrical shut-off on the battery, will make sure I have the electrical system inactivated before I start probing around up in all those wires.

Thanks, again, all! I'll keep you posted, for sure!

Cheers!!!

Dugly :cool:

If it has blown the fuse----------it will probably blow the next one also because there is a short or overload somewhere

honestly i wouldn't use either, fuse protect it at a spot that you can get at remote from the switch. cole-hersee has those also, its what i have in my car.
and there isn't a relay per-se, its more of a thermal switch. you could install a separate relay to remove the load from the switch. the initial turning on of the switch is when the fuse probably lets go from the load. so a relay may prevent it from happening again

Well, I can't say that I know how it happened, but I can say it is repaired and the car is on the road again.

Getting the burned-out fuse out of the light switch wasn't hard, but getting the new fuse in proved to be impossible...found out that it got much easier if I just took the entire switch out of the dash, didn't need to be disconnected from the wiring, just rotated so that the fuse location was easier to get some leverage on. The lights still would not work after the fuse was replaced in the light switch, and my S-O said something about maybe the other fuse was burned out so I checked. Sure enough, both fuses were burned out, the main 20 amp fuse at the fuse block and the glass tube 15 amp fuse on the light switch. I figure perhaps a power surge from the alternator, I don't know, but I have put about 5 hours on it now using the lights, switching them on and off, high beam down to low beam and back up, using flashers and high beams at the same time, everything I could think of that might overload a weak spot in the circuit and cause a repeat of the problem, nothing did. The lights are rock steady, no varying brightness with increased RPMs, they work every time. I did keep extras of each of the fuses so that should the problem repeat itself I am ready, but for now I can't imagine it happening, things are working well just as they were before the failure...but, isn't that the way it always works?

I'm not getting over confident, just hopefully optimistic.

Will resurect the thread if anything comes about, but for now life is good again in the Cobra!

Cheers, and thanks to ALL!

Dugly :cool: