Proheat M125 - Manual (Page 69)

MOTOR Diagnostic Code 12
Indicates that a short circuit, over-load or an open circuit fault is detected in
precheck (motor is not running in pre-check). During operation (motor is
running) indicates that the motor RPM is under or above target speed for
more than 60 seconds.
Troubleshoot the Motor diagnostic code based on:
1. Motor – mechanical.
2. Motor or G-II PCM – electrical.
Test Procedure – Motor mechanical function:
a) Disconnect all harnesses at the G-II PCM.
b) Disconnect the fuel supply line.
c) Remove blower housing (2) screws and blower housing. Look at blower
housing and combustion air blower for any rubbing marks.
If blower housing/combustion air blower rubbing is observed. Replace
combustion air blower.
d) By hand, rotate the combustion air blower and feel for mechanical binding.
If mechanical interference is felt, isolate the Motor from the Fuel Supply
Pump and Air Compressor by removing the Motor. Go to Motor replacement,
page 4-33. Then rotate the motor by hand checking for mechanical binding.
If the Motor spins freely and there are no obvious mechanical problems,
check the Motor/G-II PCM electrical connection. Go to Test Procedure –
G-II PCM and motor connector and harness.
Test Procedure – G-II PCM and Motor Connector and Harness:
a) Disconnect the Motor connector at the G-II PCM.
b) Inspect G-II PCM motor pins for damage or corrosion.
c) Inspect motor harness and connector for damage or corrosion.
d) Reconnect the motor harness, install the blower housing, connect the
power and switch harnesses at the G-II PCM.
e) Switch the PROHEAT on.
If Motor diagnostic code is still indicated, Motor is faulty. Go to Motor
replacement, page 4-33.
4.1.13
(12 Flashes)
Figure 4-34: Motor Mechanical Check.
COOLANT PUMP
SWITCH INPUT
DUAL MODE TEMP
SENSOR
POWER
FUEL INLET
BLOWER
NOTICE
All plugs/harnesses must be rein-
stalled into the G-II Proheat Control
Module (G-II PCM) before heater
goes back into service.
4-32 PROHEAT M-SERIES G-II PCM SERVICE MANUAL