Determine which activator(s) fail to work by applying pressure to them. Then, remove the two 15mm screws that hold the activators in place by using the Philips Head 2 screwdriver.

Only two of the three activator tabs have green micro switches that actually turn on the motor. Use a circuit tester on the power chord and press the two micro switches simultaneously to see if they complete the circuit. If not, one or both need to be replaced.