TO-20 Starting Problems...

Tom Bowman · Oct 7, 2017

The trouble started a month ago when I washed the TO-20. (I posted another thread on that.) I thought I had narrowed it down to the gearshift start switch, so I replaced it a few weeks ago, and it worked fine for a while.

Today, it wouldn't crank again.

FYI: It's a 12-volt conversion, with a one-wire alternator.

1. I have voltage to the "hot" side of the switch, BUT: when I operate the shift lever, voltage on the hot side of the switch drops to zero, which didn't seem right. (The starter does not crank.)

2. When I move the shift lever to the start position, I'm not getting voltage through the switch, to the "starter" side of the switch. The starter doesn't crank.

3. I can unhook the battery cable (at the battery) and I get continuity through the switch, when I operate the switch lever.

4.The switch terminals are not shorted to ground.

5. When it doesn't crank, I think I can hear a small arc/pop, but only the first time I hit the start lever.

What's going on? I admit, automotive electric systems are not my thing. Thanks.

miner09 · Oct 7, 2017

May be loose battery cable or wire connection.Try and find arc-pop.

CKain(MI) · Oct 7, 2017

the wire coming to the start switch has a very bad connection somewhere. voltage can go thru and can be measured(no load) but try to get the current(amperage)required to run the starter and the bad connection rears it's head. also check it at the other end, when trying to start.

for instance, I had a 'not charging' issue with my TO30. the 2 wires connected on the generator looked fine. however when I tested the voltage, it was there on the wire terminal but could not be measured on the threaded terminal coming out of the generator. Even though the connections were tight, the metal was oxidized and no actual electrical connection. Just had to 'sand' them clean.....

Steve@Advance · Oct 7, 2017

You've definitely have a bad connection on one of the battery cables.

Testing under load, like you did on the hot side of the switch, is the way to find the problem. If you can get an assistant to help hold the starter switch in while you test for voltage, you can quickly track down the problem.

Start the test directly on the battery posts, then start moving out from there. Just be careful, it could start cranking at any time!

The obvious places to look are battery cable connections, the cable ends, especially if they are the clamp on replacement type, and if the ground cable is still connected to the sheet metal, try moving it directly to the engine block.

Tom Bowman · Oct 9, 2017

Thanks for your help, guys - you nailed it. I cleaned up the negative battery cable connection at the dash, and it started right up.
Where's a good place on the engine to move that connection?
Thanks again.

John Deere D · Oct 9, 2017

Picture of FERGUSON 6 VOLT system:

After running Battery Cable as per picture STARTER / Engine spins over perfectly:

Bob...Owner operator Ferguson....6 VOLT Starter.....

TO-20 Starting Problems...

Tom Bowman

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miner09

Well-known Member

CKain(MI)

Well-known Member

Steve@Advance

Well-known Member

Tom Bowman

Member

John Deere D

Well-known Member

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