Curtis PMC 1209B/1221B/1221C/1231C Manual
28
TROUBLESHOOTING & BENCH TESTING
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C A U T I O N
Working on electric vehicles is potentially dangerous. You should
protect yourself while performing the diagnostic tests by jacking up
the vehicle to get the drive wheels off the ground, opening the battery
circuit before working on the motor control circuit, wearing safety
glasses, and using properly insulated tools (see page 2).
Sluggish Vehicle Behavior
Loss of power will be noticeable when the batteries become overly discharged.
This is a normal response to low battery voltage. Curtis PMC 1209B/1221B
controllers are designed to protect against damage caused by low batteries. On
24–36 volt models, power to the motor is cut back when the voltage goes below
16 volts. Refer to the specifications (Appendix C) for other models.
Hot Controller
If the controller gets hot, it does not necessarily indicate a serious problem. Curtis
PMC 1209B, 1221B, and 1221C controllers protect themselves by reducing
power to the motor if their internal temperature exceeds 75°C (167°F). The
1231C controller begins reducing power at 85°C (185°F). Power output will be
reduced for as long as the overheat condition remains, and full power will return
when the unit cools.
In typical applications, overheating will rarely be a problem. However,
vehicle overloading may cause overheating, particularly if the controller is mounted
so that heat cannot be conducted away from its case or if other heat-generating
devices are nearby. If thermal cutback occurs often during normal operation, the
controller is probably undersized and should be replaced with a higher current
model.
IN-VEHICLE DIAGNOSTIC TESTS (TROUBLESHOOTING)
These tests require a general purpose volt ohmmeter. You can use either a
conventional “V-O-M” or an inexpensive digital voltmeter.
The troubleshooting chart (Figure 18) serves as a guide to the procedures
that follow. Before starting these tests, refer to the appropriate wiring diagrams
and make sure your controller is hooked up properly.
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