Using an analog voltmeter (digital will be erratic because of ignition interference), connect the positive lead to ground and the negative lead to ARM on the regulator. Run motor at say 1500 rpm and touch Field lead from regulator to ARM terminal on regulator - should read at least 7.5 volts or more. Run this test not over 5 secs. If no reading, the fault is probably in the generator and if you do get a reading, then probably the regulator needs to be adjusted or replaced.
