Hey all,

This is kind of a long explanation so bear with me. Recently I installed both a modern radio (removable faceplate) and a Haneline gauge cluster in my 1968 coupe. The radio is only connected to the 12V constant power (I have to turn it on/off independently from the ignition). The cluster is connected to both 12V constant and switched power.

Everything worked fine for the first couple weeks. A couple days ago, I may have left the radio on (I honestly don't remember) and when I went to start the car the next morning it was totally dead. I got a friend to jump me and spent about 20 min trying to induce a charge to the battery. As the car was running I started testing the lights to see if everything still worked. When I went to turn on the headlights they came on for a split second then went out. The battery was relatively old and I figured I would get a new one and see what happened. After installing the new battery the headlights still refuse to turn on. Everything else works fine. The brake lights, front turn signals, radio, gauges, dash lights all work.

I pulled the dash apart but couldn't find anything that stood out to me. Anybody have any ideas why my headlights won't turn on? Are they fried maybe?

 

I'm sure you have already check all of the fuses. Is it possable that you got a voltage surge and blew the headlight filaments out. Does the bright settings work? Also it's possable that something is wrong with the switch itself.

 

Yeah I checked the fuse block and they were all fine. Headlights don't work at all on low or high beam. Also tried to check the switch but i couldn't find anything that really caught my attention. When i pull the switch all the way out i can still dim and brighten the dash lights and the brake lights come on. I'm leaning towards thinking the headlights are blown but I don't know how and that would suck. Still holding out for an easier wiring issue that I can find.

 

A grounding wire from the headlight harness. Headlights have two filaments. I don't think both would blow unless the bright light switch was on.
You can always check for power at the harneses using a simple circut tester.

 

The headlight switch in early Mustangs are notoriously weak. They contain an internal circuit breaker which is often the cause of headlight problems. Yours could be toast. I'd pull out the switch and put it in a vise and use your multi-tester and check for functionality. Do you have a wiring diagram for your car? If not, get one. Very handy.

I went a step further and isolated my headlight switch using relays so the switch itself is only exposed to milli-amps instead of 20amps.

 

Yup that solved it. Bought a new headlight switch from Autozone and everything works again. Thanks

 

I didn't know you could buy a headlight switch for a 68 at AZ

 

Neither did I until I saw it mentioned in another thread somewhere. They look identical and its a very easy remove/install. Did the whole switch in 5-10 minutes. $20 for a new one.