Curtis PMC 1209B/1221B/1221C/1231C Manual
32
TROUBLESHOOTING & BENCH TESTING
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C A U T I O N
3-C While you have the potbox wires off the controller, use an ohmmeter to
check for shorts between these wires and the vehicle frame. You should see
a resistance of at least 1 megohm. If it is lower than that, inspect the wiring
for damaged insulation or contact with acid. If necessary, replace the potbox.
3-D Push the wires back on the controller terminals. It doesn’t matter which wire
goes on which terminal.
3-E Inspect the terminal area of the controller closely. Occasionally a buildup of
dirt or acid residue of a conductive nature causes electrical leakage between
the throttle input terminals and the B- or M- terminals, leading to faulty
controller operation. To check for this problem, measure the voltage at the
appropriate throttle input terminal (the upper terminal for 0–5kΩ pots, the
lower terminal for 5kΩ–0 pots), by connecting the voltmeter (-) lead to the
controller’s B- terminal. The keyswitch must be on and a direction selected
for this test.
THROTTLE INPUT VOLTAGE (in volts)
STANDARD
0–5kΩ POT 5kΩ–0 POT
UPPER TERMINAL LOWER TERMINAL
Zero throttle: 2.7 3.1
Full throttle: 7.0 7.4
Compare your readings with these; if they are different by more than a few
tenths of a volt, contamination is probably the cause.
3-F Carefully clean off the terminal area of the controller with a cotton swab or
clean rag moistened with water, and dry thoroughly.
Be sure to turn everything off
before cleaning.
Now test the controller to see if proper operation is restored. If so, take steps
to prevent this from happening again: dirt and water must be kept from
reaching the terminal area of the controller. If the voltages are still out of
range, the controller is at fault and should be replaced.
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