need a detailed wiring diagram of all the wires going to the headlight switch. the illustration in the 34 shop repair manual isn't too detailed. looks like there is a resistor that is fastened to the headlight switch but this NOS headlight switch lacks the resistor. and the gauge restoration shop used by a previous owner has a resistor on the gas gauge. when i put voltage from battery to starter and fire the engine up, the wire from the generator field to the headlight switch becomes shorted out(hot and melting insulation). the generator cut-out device is bench test functioning properly . any help will be appreciated. mike mccagh
The electrical system on these cars is a one wire system to ground. If the wire to the headlight switch is grounded then it will draw all the current it can. Remove the wire from the headlight switch and at the generator. Place a volt ohm meter with one tip on the wire and the other on a good solid ground. If you get a reading making a circuit then the wire itself is "grounded". Look for a place where the insulation has worn through. Repair or replace the wire. If you do not get a reading with the wire disconnected then the wire is good. Look at the switch itself. With the headlights off check to see if by placing one tip on the place where the wire that is getting hot hooks to and the other to a good ground. If you get a reading then the switch is bad. Remove all wires that go to lights from the switch and re-test the switch in the off position. If it shows a reading then the switch itself is grounded. This proves the switch is bad. It is simply a matter of isolation by removing one at a time and testing. Remember it is a one wire to ground system.
Mike, i believe the field terminal on a 34 generator should be connected to ground through the headlight switch. When the OEM switch is in the off position the ground goes through a 1 ohm resistor on the back of the switch reducing the generator output. When the switch is full on, the resistor is eliminated form the circuit causing full generator output. When my resistor burned out i just grounded the field terminal to the generator case until I replaced the resistor. The wire from the output side of the cut out is connected to the fuse terminal on the back of the OEM headlight switch and from there goes to the amp meter. I can send you a couple pictures of an OEM switch if you need them. Hope this helps.
i'd really appreciate a photo of an original 34 master headlight switch as the NOS one off ebay has no 1 ohm resistor on its backside. so if i run a pigtail wire from the field terminal on the generator to a good ground, that'll prevent the repo harness wire from field to incorrect for 34 headlight switch, all will be ok, even using the non-34 headlight switch. i assume i'll have to remove the field repo wire from field to incorrect headlight switch. damn, with i had an original 34 headlight switch as it seems that would solve my problems . big thank you to yourself and terrill. i'm getting frustrated being unable to solve this problem. mike mccagh
terrrill: unlikely that the wire from generator field to the non-34 headlight terminal i choose to fasten it to would be bad as its a brand new Harness Unlimited setup that came from the previous owner. since there is no 1 ohm resistor on the NOS ebay headlight switch, i suspect therein lies the problem. anybody got a 34 headlight switch that has the 1 ohm resistor attached to it? thanks again guys. mike
Mike, Here are two pictures of an original headlight switch that I copied from EBay a few years back. The same switch is in my original 34 Master. The field wire connects on the back side to the resistor while the wire from the cutout connects to the fuse terminal on the other side of the switch. And yes, you should be able to just ground the field terminal to the generator case (one of the screws holding the cutout on).
mike: i'd appreciate a photo of an OEM 34 headline switch and if possible take closeup of the various letters embossed in the bakelite of the switch. thanks, mike
Mike, The only pictures I have are those posted. As mentioned, I copied the pictures from EBay when I was looking to replace or repair the burnt out resistor on the switch in my car. I bought a 5 pack of 1 ohm resistors from Amazon and repaired my existing switch in place. The link to the post below shows a picture of the repair. I can send you a resistor if you want that you can wire in series to your field ground until you find the correct switch. Generator output will be reduced which should be correct for daytime driving.
mike: photos of your headlight switch were very helpful in identifying the appearance of an original 34 master headlight switch. I'd be happy to pay for one of the resistors you got from Amazon. mike mccagh 12500 mason rd cumberland ,md 21502. thanks again, mike
Mike, I have a resistor 1-5/8 inches center to center. Too big? I tried to measure the resistance but got zero. I'll send it to you if it is the right size to fit.
