Once you get past around 18/20 volts with the common cheaper 12 rated starters and applying good loads from a recalcitant larger engine and yes on cold days You will reach a point where they start failing and its not in the way you might expect in the windings or such.

What seems to be the first point of failure when such loads are applied and that type of current is demanded on the cheaper starters, it is the switch that will fail Especially the type that are made with that tiny contact point on the spring plates. Some have a larger diameter point set on the plates and these fair better.

Another switch plate set I just discoverd has no points at all and one of the spring plates is punched to form a long tang of the plate itself that serves as the switch contact. I am now just experimenting with this type and like it so far.

Anyway what happens when to much current is demanded of that tiny contact point on many of the switchs it will weld itself together and the motor will not shut off.

John

Oh and the dynatron starter mentioned earlier is of course rated at 24 volts so not much help for Popriv's question about his inexpensive 12 volt unit.