Motrec T-448HD, Operator And Maintenance Manual

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Maintenance
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NO MOTION
Make sure that the PMC surface is clean and dry; check the terminal areas. Dust Particles or acid
contamination, can create current leaks and cause a PMC malfunction.
Check F/R switch
Turn on the key switch and set to forward. Check voltage between the forward terminal and the
– terminal on the battery gage, check voltage between the reverse terminal and the – terminal on
the battery gage; if both B+, replace the F/R switch.
Check switches and wiring
Disconnect control terminals on the PMC and check all control signals. If a switch pin does not
read B+, check wiring or replace the switch.
Check potentiometer
Turn the key switch to OFF, disconnect potentiometer terminals. Check the resistance across
terminals: if not within the recommended limits, adjust or replace the potentiometer. Check for
shorts between potentiometer wires and vehicle frame; resistance should read at least 1
megohm.
Check main contactor or solenoid
Check voltage across power terminals; if not B+, check circuit breaker or replace the solenoid.
Turn to on the key switch and activate the seat switch. Check voltage across the coil terminals;
if not B+, check wiring and interlock switches. Check resistance across power terminals; if not
0 ohms, replace the solenoid.
Check circuit breaker and SEPEX DIODE
Before replacing the circuit breaker, check for shorts in the power circuit and check the SEPEX
diode in the power circuit using a diode tester. If no such instrument is at hand, use an
ohmmeter: the reading should be weak in one direction and strong in the other way.
Check the resistance across the circuit breaker. If not 0 ohms, replace the circuit breaker.
Check PMC
First disconnect battery B+ and B-, then PMC B+ and M-. Check the internal diode between B+
and M- terminals using a diode tester. If no such instrument is at hand, use an ohmmeter: the
reading should be weak in one direction and strong in the other way. If the internal diode is
defective, the PMC must be replaced.
Check the Motor
First disconnect battery B+ and B-, disconnect power terminals and check the motor armature
and field for opens.