Proheat X45–School Bus - Manual (Page 92)

5-35 SECTION 5. TROUBLESHOOTING & REPAIR
FUSE
If, when the heater is switched “ON,” the heater does not run and the “ON”
light does not light, check the fuse in the PCM. The fuse will blow if there is a
short to ground in a positive lead or internally for the following components:
• ON/OFF Switch • Coolant Pump
• Air Compressor/Fuel Pump • Blower
• Ignition Coil • Internal Wire Harness
Reversing polarity at the battery will also cause the fuse to blow. This will not
harm the PCM.
Check: Heater wiring. See flow chart Figure 5-28 on next page.
Figure 5-27 Internal Wire Harness Test
F
E
D
C
B
A
3 2 1
3 2 1
HARNESS TO
COMPONENTS
PIN LOCATIONS MOLDED
INTO CONNECTOR
COIL
COOLANT PUMP
COMPRESSOR BLOWER
GROUND ON
HEAT EXCHANGER
FUSE
CAUTION
Repeated replacement of the fuse
or using incorrectly rated fuses
without correcting the problem,
can damage the PCM.
5.2.8