Just a hint about immediately popping fuses when looking for a short or overload in equipment.
This is for when the equipment is in the shop and when you install a fuse it blows immediately or while.
If you cannot see the short using a ohmmeter and sometimes you cannot find with Ohms readings and the short or overload is almost immediately after the fuse is installed.
I keep some of the DC thermal Overload breakers around, the stud type from 5, 10, 15 amps and on up.
I have a clamp on automatic scale DC ammeter that goes up to 400 amps, I clamp it around the wire with the thermal breaker installed and test. I can confirm the overload or short without blowing fuses using the breaker and also I can move the breaker to different circuits (wires) to find the direction of the overload/short. Just be ready to disconnect the breaker fast if the overload is excessive as indicated on the ammeter to keep from burning wires.
Kinda disgusting and costly to just keep blowing fuses when trying to find a equipment overload especially if it the erratic type. With the intermittent erratic type shorts/overloads I have had to place a fuse in different circuits to get an idea of the direction of the overload
for example in your case fues just the electric clutch circuit with a 10 amp fuse and see if it blows before the 15-20 amp so as to get an idea if it's the clutch.
Also it's usually not mentioned in the troubleshooting to OHMs test the clutch coil winding to case ground with both wires disconnected so as to see if the coil winding is grounded internally.