Fuse blows even when key off

zaugger

zaugger

Member
I was driving a 1929 Model A when the engine just stopped running. Put a new fuse to the starter, (it was blown) car started and started running again. For about 30 feet. Blew again. Now, even if I set a fuse on top of the connectors it explodes. Any thoughts? Thank you!
 
Thanks so much. I did exactly as the PDF said, and everything was fine until I added the light bail. Adding the light bail blew the fuse. When I disconnected the light bail and put in a new fuse it’s still blew. So I’m wondering if there’s an issue with the cutout or the generator itself? Any thoughts? Is there a way to test?
 
Yep. Separated it and cleaned it it. It did start for about 5 seconds after that before it blew. But then I disconnected the bail and a new fuse blew right when I put it in.
 
Ok. It’s magic. I reconnected everything and remembered it happened just after I was breaking. My friend who i am getting the car from mentioned he has replaced the brake switch several times. He looked underneath the car and the switch was open when it should have been closed. Disconnected the switch and bingo. Starts and stays lit. Any solutions the the continuing brake switch saga? Anyway, thanks SO MUCH for your help!
 
The brake switch has power to it at all times that comes from the light switch bail. When you step on the brake, the power gets extended from the switch to the brake light in the tail light assembly. So, if it blows only when you step on the brake, then the output of the switch (the green wire that goes to the stop light is shorted somehow. It could be that the switch post itself is grounded, the green wire leading to the stop light could be frayed and grounded, or the stop light socket in the tail light assembly could be shorted to ground. Also, the switches themselves aren't foolproof. The short could be in the switch itself.
 
Keep in mind that on the Model A the ignition switch only turns on the ignition, and only the power to the points at that. Everything else will have power when the battery is connected.
 
Most likely it has a bad repro brake switch that grounds out. Disconnect both brake switch wires then connect an ohm meter from each terminal to ground and try the switch both off and on to see if either terminal connects with ground. If it does then you can take it apart and correct the problem.
 
mine was blowing because under the speedo amp fuel gauge housing a wire was just barely touching the rear of the tank area, also refreshed the fuse link on starter with a quality made one.
 
Thanks, all. I may have some other issues, but for now I replaced the brake switch and no longer have the short.
 
Now take the switch apart and find the rest of the story. It is a simple thing, contacts and insulation to isolate a wire that is hot.

Troubleshooting is finding the location,cause and correction using a schematic and logic with simple tools like a test light. This is just the beginning, prepare for the future.
 
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