I don't often recommend this, but jumper the seat switch if you don't have an assistant. Select a 40 VDC minimum scale on your multimeter.Place the multimeter leads on the armature terminals.{This is one time where having a sand based meter is a plus. You don't need to be concerned with polarity.}
Advance the throttle to a Forward position. Observe voltage reading if any.Less than 36 volts is to be expected if the armature resistors are in the circuit.(Speeds 1 & 2.) No reading ? Place the throttle in Reverse and repeat the test.You should have a reading since Reverse was functioning.If that's the case, you will probably be replacing armature contactors.
Please report your findings. <G> dick both wrote:
Have multimeter. Have schematics.