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Curtis PMC 1204/1205 Manual
TROUBLESHOOTING & BENCH TESTING
the flow: 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.
2-E If the contactor coil and KSI are getting voltage, make sure the
contactor is 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.)
TEST
3 Check the potbox circuitry
The following procedure applies to the standard throttle input configura-
tion 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 configura-
tions. Some 1204/1205 controllers are sold with other input characteris-
tics. 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.
3-A With the keyswitch off, pull off the connectors going to the throttle
input 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:
RESISTANCE (in ohms)
STANDARD
0–5kΩ POT 5kΩ–0 POT
Pedal up: 0 – 50 4500 – 5500
Pedal down: 4500 – 5500 0 – 50
3-B If these resistances are wrong, it is because the pot itself is faulty, the
wires 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
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