Model A Electrical Gremlin

[Amctavish77]

I have a ‘31 Tudor that I’m having an odd electrical issue on. A couple weeks back, the horn wires were removed from the back of the horn and inadvertently made contact with the headlight bucket resulting in fried horn and headlight wires; only about 6-8” of wiring was lost. But, it resulted in the car not starting either. I seemed to have figured out the starting issue however, I still have an electrical gremlin causing an issues.

When I can get the car to run, if I flip the headlight selector on the steering wheel to the left (lever arm towards driver door) the car will die and not restart. It seems to kill power throughout the entire system. It did it twice yesterday, the first time I was able to get it fired again but not the case the second time.

Could the headlight switch be bad? Or is there something that I am missing all together! The Model A electrical seems relatively easy so I feel like I’m overlooking something!

[ModelA29]

Sound like the wires also melted somewhere in the loom and are causing a short. Get out a meter and start checking that 2 aren't melted together.

[nkaminar]

How handy are you with electrical systems? If you are not handy then get some help. If you know how to use a multimeter then do the following:

Disconnect the wire going to the head light switch at the cutout on top of the generator. Remove the headlight switch. Set your multimeter to the ohm setting. It doesn't matter which ohm setting but somewhere around 25 ohms. Clip or clamp one lead to a good ground point. Test the ground connect by taking the other lead and putting it on another ground point which should register a very low resistance. Now take the other lead and put it on one contact in the light switch. If it reads a high value then that wire is OK. If it reads a low value, somewhere less than one ohm, then there is a short in that wire or the connector at the end of that wire. Repeat for all contacts. When you find the short, trace out the wire to the end, such as the socket that holds the light bulb. Fix whatever is bad, such as replacing wires or repairing a connector or socket.

[Amctavish77]

Nkaminar: thanks for the reply. This car is outfitted with a GM style alternator; does that make a difference of where I should be looking?

[Tom F OHIO]

Originally Posted by Amctavish77

Nkaminar: thanks for the reply. This car is outfitted with a GM style alternator; does that make a difference of where I should be looking?

Does the car die when you turn on your headlights? If not then keep in mind that when you turn the switch to the left that is your parking lights. Somewhere a wire for the parking lights is touching together and causing a short and its probably the wire going to the bucket that has caused all the problems.

[Amctavish77]

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Tom: all the wiringin the headlight buckets look good, nothing fried, crossed, frayed, etc. I made a couple discoveries though; when the headlight switch is moved to any of the position, it’s seems to kill power to the whole car. If it’s in the off position, I have power everywhere however, the car will still not start (it’ll turn over but no fire.

Which leads me to another dilemma, how can I have voltage at the points (in the open position) but no spark? I have voltage at the coil, the terminal box, bottom plate of the distributor, and at the points but no spark. Points are clean and gapped properly but no spark when I open them.

This whole thing is driving me ������

[jrelliott]

When you close the points, does the voltage go to zero? If it goes to zero then you have completed the circuit and you should get a spark when you open the points again. Also check the condenser. When the light switch is engaged, and everything dies, you have a short somewhere. Use the ohm meter as suggested above to find the short

[rotorwrench]

The horn is generally connected to the power off the generator as a power pathway. The other wire from the horn is connected into the headlight switch mechanism so that the ground path can be functional as the switch to complete the current and ground path circuit for it to function up through the horn rod inside the steering shaft. If the one hot wire off the generator touched ground then it would create a hot wire short and would damage that wire and any wire it happened to be touching. If something shorted across to the headlight circuit then it could also damage wiring or connections in that circuit as well. This is a good link for all sorts of wiring inspection and checks to include the horn and headlights.
https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

A direct short anywhere can draw enough current to kill the engine. Those wires are 16 gauge but they don't pass current well if there is a short anywhere. It might be worth getting the alternator checked out as well. A short directed to it could damage to the diode bridge.