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Curtis PMC 1204X/1205X/1209/1221 Manual
1. First, check both sides of the control wiring fuse.
2. Check both sides of the polarity protection diode to make
sure its polarity is correct.
3. Check both sides of the keyswitch.
3. Check both sides of the pedal microswitch.
4. Finally, check the contactor coil and controller KSI.
If the contactor coil and KSI are getting voltage, make sure the contactor is
2-E
really working by connecting the voltmeter across its contacts (the big
terminals). There should be no measurable voltage drop. If you see a drop,
the contactor is defective. (We assume the recommended precharge resistor
is in place.)
3
Check the potbox circuitry
TEST
The following procedure applies to the standard throttle input configuration for
these controllers, which is a nominal 5kΩ pot connected as a two-wire rheostat (0
= full off, 5 kΩ = full on), and also to 5kΩ–0 configurations. If your installation
uses a controller with a throttle input other than 0–5kΩ or 5kΩ–0, find out what
its range is and use a procedure comparable to the one below to make sure your
pedal/potbox is working correctly.
With the keyswitch off, pull off the connectors going to the throttle input
3-A
of the controller. Connect an ohmmeter to the two wires going to the potbox
and measure the resistance as you move the pedal up and down. The
resistance at the limits should be within these ranges:
Pedal up:
Pedal down:
If these resistances are wrong, it is because the pot itself is faulty, the wires
3-B
to the pot are broken, or the pedal and its linkage are not moving the potbox
lever through its proper travel. Actuate the pedal and verify that the potbox
lever moves from contacting the pedal-up stop to nearly contacting the
pedal-down stop. If the mechanical operation looks okay, replace the
potbox.
TROUBLESHOOTING & BENCH TESTING
(in ohms)
RESISTANCE
STANDARD
0–5kΩ
5kΩ–0
POT
0 – 50
4500 – 5500
4500 – 5500
0 – 50
POT
29
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