Floor Starter Switch - Help Please

[glennpm]

Hi,

I'm close to starting my 1932 roadster for the first time and ran into a problem with my foot operated floor switch.

- I have a hopped up 59A.
- 12 volt negative ground
- Brand new 12V group 34 battery
- stock replacement cable form switch to starter
- #1 welding cable to other side of switch back to positive battery terminal
- master disconnect which disconnects ground
- car not running yet and ignition was off at all times during this test
- Think the switch was NOS but bought it so long ago, I'm not sure. Made in USA stamped on bracket.
- Copper plates in switch welded together, cracked.
- No sign of arcing inside or outside switch
- Insulation on starter operating post is now damaged.

When I first tried turning over on Saturday, it cranked but maybe a little slow. I removed the plugs and cranked it for five or ten seconds a couple of times. I then smelled burning and switched the master disconnect off.

The starter switch was very hot. All the wires were tight to it and not even warm. Starter was cold to touch too. No evidence of arcing with any of wires around switch. Tried it again yesterday and same problem. This morning I removed the switch and took it apart and it is toasted!

Looking for help in what the issue may be and wondering if I need to change this over to a solenoid operated arrangement which I'm not keen to do.

Appreciate help please.

[51 MERC-CT]

Will it turn over without any issues if you connect the two leads together?
If it does turn over then it looks like a direct short in the switch to the outer grounded case.

[glennpm]

Yes, spins nice and fast and no issues with the two leads together. I completed the circuit with my master shut-off switch.

[51 MERC-CT]

Originally Posted by glennpm

Yes, spins nice and fast and no issues with the two leads together. I completed the circuit with my master shut-off switch.

Sure looks like a direct short from the battery side to the grounded box.
Perhaps the stud insulators on one side or the other are defective.

[glennpm]

Yes but before my starting attempts, there was no direct ground otherwise my amp meter would have shown a huge discharge. I think I checked this morning for continuity and there was none from post to case but not sure. Kind of hard to tell now and especially since the insulation around the push rod post got burnt up some too. King figure why a brand new switch would have done this. There is no binding through the floorboard either that would have knocked the post over.

[51 MERC-CT]

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Originally Posted by glennpm

Yes but before my starting attempts, there was no direct ground otherwise my amp meter would have shown a huge discharge. I think I checked this morning for continuity and there was none from post to case but not sure. Kind of hard to tell now and especially since the insulation around the push rod post got burnt up some too. King figure why a brand new switch would have done this. There is no binding through the floorboard either that would have knocked the post over.

Yes, if the battery side was not grounded you would not see any amp meter indications. But, if the starter side had the short, as soon as the pedal was depressed, guess what would happen.

[glennpm]

Yes you're right. I guess it is just a bad/new switch. I have a used original coming to me now. I just don't want to destroy another one. These switches are supposed to be good for large amperage.

Thanks

[Bruce Lancaster]

Stamped "40"...I think most of the NOS '32 switches around are these '33-4 ones. If my memory is correct, bracket has to be bent a little to position them correctly...maybe the bending shifted the innards and allowed the contacts to touch the case? On the new one, disassemble and check everything out. If a used switch, I think you can rotate the studs to put clean surfaces in contact. As you say, the switch should have no problems with the amperage in use.

[glennpm]

Yes it is stamped "40" and I think from 33-34 too.

The trouble with disassembly is that the tabbed locking washers, two per stud won't rotate off, have to be pried and does a number on the soft brass studs. Maybe there is a trick to this? The case tabs bent over without too much trouble and can be bent back good it seems.

The one coming is used, and I'll check continuity. Thinking back this morning I checked stud to stud and they were connected. This made me decide to disassemble it. I didn't check stud to case or stud to push rod and probably should have. At this point though, it was already wrecked.

Thanks,
Glenn

[koates]

Glen, looks like the short to ground was in the round insulator in the centre of the copper bar moving contact. The two threaded stud contacts and insulators are OK. You don't remember the history of this switch so it was likely faulty before you fitted it to your car. Fit a NOS switch (plenty on ebay) and you will be good to go. The used switch you are getting could be a gamble on quality. Regards, Kevin.

[glennpm]

Thanks Koates!

I just bought one off of Ebay for only $20 US plus cheap shipping and less than the used one. I may return the used one which was from a vendor that I do lots of business with.

Glenn