full speed or nothing at all

rob, sounds like your switch needs to be replaced. "switch handles all on/off and variable speed functions. They also have a role in electric breaking; they can momentarily reverse electrical polarity. Because switches use mechanical internals, they tend to degrade and wear out over time, eventually requiring replacement. Some common signs of a broken or failing switch are:

The tool will not start when you use the switch, or it requires multiple tries to turn on, until eventually it refuses to start at all.

The variable speed function and electric braking aren’t working properly." this and a new switch from here. Hope this helps, good luck.