Proheat X45–School Bus - Manual (Page 84)

5-27 SECTION 5. TROUBLESHOOTING & REPAIR
A COOLANT PUMP 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 motor. This component is ground side switched in
the PCM.
The coolant pump is not self-priming. Ensure that the coolant system has
been purged of air by running the vehicle engine for at least ten minutes
following installation or service. (DO NOT run dry.)
Symptom: Pump not running (code indicated)
Check: Pump Motor
a) Connect coolant pump directly to the rated voltage
(12/24 Volts) and see if it runs. If not, replace the pump.
b) Measure coolant pump motor resistance. Using a
multimeter, measure the resistance across the coolant pump
connector pins. If resistance shows an open circuit or an
internal short circuit, replace the coolant pump.
c) Measure coolant pump current. Use test lead part #967921K
as described on Service Bulletin #967329 in Appendix.
11 Coolant
Pump
Figure 5-24 Coolant Pump Test
MODEL CURRENT DRAW (Amps)
X45-12 1.50 - 4.00 @ 12 Volts
X45-24 0.75 - 2.00 @ 24 Volts