12 volt wiring at the ignition

RJMiller · Oct 28, 2009

I am looking for a wiring diagram for the ing. switch. 12 volt. on a 1955 Farmall 300. Having problems at the ing. switch. The tractor starts when I let OFF of the key while trying to start

Thanks

Bob

Janicholson · Oct 28, 2009

The issue may not be the key.
If it will crank with the key in the start position,
and will run (if it fires when the key is turned to run) in the run position, it may be OK.
Most key switches maintain the ignition connection when starting because it is not a separate switching action.
The ignition coil may not be firing while cranking because of low voltage to it.
Low voltage can be caused by a weak battery.
A set of too small battery cables (00gauge is needed, including ground strap)
a out of spec ballast resistor (if it has one)
a poor coil
12 v coil with no external resistor required used with a ballast resistor.
or combination's of these issues.
A 6 volt coil needs at least five volts when cranking (it will have an external resistor)
a full 12v coil (No resistor required) needs at least 10 volts when cranking.
A 12v coil that needs a resistor is just like a six volt coil in reality, and needs 5v at least when cranking.
If there is voltage when cranking, it is the amount that is an issue. If none, it might be the key. Good luck, JimN

12 volt wiring at the ignition

RJMiller

New User

Janicholson

Well-known Member

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