The plot thickens....I recheck all my grounds and headlights are working fine. I drive to work today, and switch from high to lows. Headlights dim, but red light stays on to indicate high beams are on.

I replace the switch, high beams are still stuck on. I test the resistance on old switch, and it works normal. Now I am really lost.

 

One problem is definitely the hi/low switch. If you look at the schematic, you'll see the hi beam indicator light is sistered with the hi beam supply at the firewall connector. Therefore, if the hi beam indicator is still lit, the wire feeding the hi beams still has juice. Were this juice is coming from is something you'll have to determine.

You might want to remove your headlights and hook up a test light there to remove them as a possible failure point. The two filaments in the headlight share a ground path so it is conceivable you have some back flow. Electricity follows the path of least resistance, so if your hi beam light is lit even on low beam, I bet your grounds on the radiator support are bad. At least I think that ground is the local headlight ground. It has been too many years.

Hope this helps.

 

Thanks! I have the drivers headlight off right now. Checking them individually now.

 

Okay, I removed both headlights and the red light indicating high beams are on and it still would not switch. I am at work right now, but I cant see the schematics on this web page below because the site is banned.

http://www.hammar.dyndns.org/~djhamm...wiring1965.htm

 

Take the hi/low beam switch out of the mix. The middle wire should be the supply and the outer wires operate the hi or low beam filament. When you direct feed the low beams, does the hi indicator still light? If so, your problem should be near the head lights themselves. Best case (read easiest) is your hi/low switch is bad which allows some current leakage across the contacts, thus lighting the indicator in the dash. But this small leakage is not enough to light the hi beams.

Weekends are for working the Hobby, not for working!!

 

I did replace the high/low switch (and the old one tested good), but I will disconnect it and jumper it when I get home. Also, are there separate fuses for the low and high beams? I didn't drive the car to work today so I cant look. I do have a copy of the schematics now and I am studying them.

Well I am broke so I am working overtime. Spent all my savings at the dentist and converting this car to run on unleaded.

 

I was testing the connection at the headlight. Right now both the low beam and the high beam have positive 12volts at the same time. So I believe that the two positive wires were being merged together. 1 ohm resistance between the high and low and the dimmer switch (should be infinity). Unplugged the wires at the firewall by the master cylinder. Became infinite resistance. Problem was in engine bay. Battery was resting against front of car and wore the wires together! Thanks for all your help!

 

Well, I was going to say to check for a short between the high and long beam circuits.... but I guess I was a touch too late...

 

Wires are delicate things, and get chafed/cut/melted/torn/abraded very easily. Seems your fix, while easy, could have been a disaster. Do you carry a fire extinguisher? Picture yourself standing on the side of the road, as your Mustang burns, wishing you had gone to Lowes for that extinguisher. Just some friendly advice.

I like JMD's signature. I bet his fan is well powered.

 

I carry a quality fire extinguisher. My friend inspects oil rig fire extinguishers and gave me one for my car. I learned my lesson when I was towing my jetski and I passed a chevy blazer on the I-40 in Little Rock on fire. I took my extinguisher from the jetski and attempt to put the car out. Yeah, no help.