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C A U T I O N
Curtis PMC 1204X/1205X/1209/1221 Manual
3. If you find the diode to be shorted, the controller is
defective.
Put the A2 cable back on the controller and reconnect the battery.
4-H
If the plug diode is okay, there is a short in the motor circuit. The short could
4-I
be in the forward/reverse switch, so look there first. Because the resistance
of the motor is so low, the motor must be tested separately if it is suspected
of having a shorted winding.
BENCH TESTING
First, before starting any bench testing, pick up the controller and shake it. If
anything rattles around inside, the unit should be returned.
Protect yourself during bench testing. Wear safety glasses and use insu-
lated tools.
Equipment Needed
The simple setup shown in Figure 18 is required for testing these controllers on
the bench. You will need:
• a POWER SUPPLY with a voltage equal to the rating of the
controller you want to test. You can use either a string of batteries
or a regulated line-operated power supply. Because only low
power tests will be described, a 10 amp fuse should be wired in
series with the batteries to protect both operator and controller
against accidental shorts. A battery charger alone should not be
used as a power supply, because without a battery load its output
voltage may exceed the rating of the controller.
• a THROTTLE POTBOX. For controllers with the standard
throttle input configuration (a 5 kΩ pot wired as a two-terminal
rheostat), a Curtis PMC potbox or any 5 kΩ pot will work fine.
For controllers with other input options, use whatever kind of
throttle is used on the vehicle.
• a POWER SWITCH to disconnect all power from the test setup.
• a MAIN CONTACTOR with a 250 ohm, 5 watt resistor across
its high-power contacts and a KEYSWITCH to turn it on and off.
TROUBLESHOOTING & BENCH TESTING
32
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