Starter motor burn out

Question

I had a diesel engine machine today, that someone had wired up a toggle switch from ignition live to the starter motor solenoid pull in connection, due to problematic sticking ignition switches.
Unfortunately, somebody connected the original starter wire from the switch, giving 2 wires pulling the solenoid in.
Eventually, the starter motor main motor burnt out.
Would the above cause that? Increased amps etc?
I'm trying to be 100% sure whether it was a sticking ign switch or the 2 wires throwing the solenoid in, that caused the burn out?
Thanks

Gary Marks · Answer

Multiple wires carrying the same 12v (assuming correct polarity) shouldn't cause a problem, since it's the solenoid itself which limits the current flow. It would be like hooking multiple wires to the same light bulb. The light bulb limits the current, not the supply wires. My money would be on an ignition switch that didn't release properly, or an incorrect connection of some other kind.

Answered by Gary Marks on August 24, 2021

Solar Mike · Answer

It probably failed because of wear, the brushes got low and the spring force was reduced so the arcing increased which caused it to get too hot.
Resurface the commutator, new brushes and springs and if the windings are still good it should be fine, check & oil/grease the bearings as well.

Starter motor burn out

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