Proheat X45–School Bus - Manual (Page 82)

5-25 SECTION 5. TROUBLESHOOTING & REPAIR
An IGNITION COIL diagnostic code indicates an open circuit in the wire
harness, a short in the wire harness between the positive and negative leads
or an internal short in the coil. The fuse will blow if there is a short to ground
in the positive lead or the coil. The ignition coil is the easiest place to
measure the voltage on the heater. This component is ground side switched
in the PCM.
Symptom: No spark at the electrode (code indicated)
Check: Coil wiring
a) Inspect the wiring harness to ensure the ring terminals are
secured to the coil. Make sure the polarity is correct.
b) Inspect for broken or abraded wires in the wire harness.
b) Test coil. (Figure 5-23.)
c) If an IGNITION COIL diagnostic code occurs and no fault is
found in the coil and wiring, then the PCM must be checked.
Symptom: Air Compressor running (No code indicated)
Fuse blown in PCM
Check: Air Compressor operation
a) Harness for pinched or abraded wires. The positive wire must
not short to ground.
b) Motor for internal short. (See Figure 5-21 and Test Procedure)
c) Check for seized motor or fuel pump. (See Figure 5-5 and
Figure 5-22)
REMOVE FOUR BOLTS AND
COVER FOR ACCESS TO THE
COMPRESSOR COUNTER
WEIGHT BY HAND TO
CHECK FOR SEIZED MOTOR
OR FUEL PUMP.
Figure 5-22 Compressor Access Cover
10 Ignition
Coil
WARNING
The PROHEAT chassis is grounded
from the PCM as shown in Figure
5-14. Ensure the ground is securely
connected. Failure to ensure a
proper ground may result in
electrical shock.
WARNING
Disconnect the PCM electrical
power prior to trying to turn the
compressor counterweight by
hand.