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TK 54343-18-MM-EN
7. Check the continuity of the T1-W, T2-U, and T3-V wires from the compressor motor contactor to the compressor
motor. If all three wires have good continuity, the compressor motor is most likely faulty.
Electric Standby Circuits
If the unit does not run in the electric standby mode use the following procedure.
Make sure the unit is connected to the proper power source.
Check the power cable receptacle for power. If power is there, check for power at the unit terminal plug.
If the compressor motor contactor is pulled down but the compressor motor fails to start, the trouble is probably in the
compressor motor.
If the compressor motor contactor is not pulling down proceed as follows:
1. Check the AC line voltage and the transformer input fuse F23. If the AC line voltage is acceptable and the
transformer input fuse is intact, go to step 2.
2. Measure the transformer output voltage (AC). The voltage reading should be approximately 12 Vac. If not, the
transformer is defective. If the transformer output voltage is acceptable, go to step 3.
3. Check the rectifier output voltage (DC) on the 2R wire at the smoothing capacitor (C1) and check for continuity to
ground on the CH wire at the smoothing capacitor (C1). If this voltage is less than approximately 12 Vdc, and if the
2R circuits to the rectifiers and the 11.5V and 0V circuits from the rectifiers to the transformer have good continuity,
the rectifier bridge is defective. If the rectifier bridge output voltage is acceptable go to step 4.
4. Check fuses F24 and F25 on the X1 and X4 wires at the transformer.
5. Check the rectifier output voltage (DC) on the X1 wire (pin B8 at Connector MP1-C1 on PCB1 in the ECM) and the X4
wire (pin C8 at Connector MP1-C1 on PCB1 in the ECM). If voltage is not present, check the continuity of the X1 and
X4 wires from the transformer. If the rectifier output voltage is acceptable, go to step 6.
6. Check the voltage on 2R-01 wire at the standby power relay. If voltage is not present, check the continuity of the 2R-
01 wire from the smoothing capacitor (C1). If the voltage on the 2R-01 wire at the standby power relay is acceptable,
go to step 7.
7. Check the voltage on the 2RB and 2RB1 wires at the standby power relay. If voltage is not present, check the
continuity of the 2RB wire. If the voltage on both the 2RB and 2RB1 wires is acceptable, go to step 8.
8. Check the voltage on the 2RB1 wire at the battery disconnect relay. If voltage is not present, check the continuity of
the 2RB1 wire from the standby power relay. If the voltage on the 2RB1 wire at the battery disconnect relay is
acceptable, go to step 9.
9. Check for continuity to ground on the CHX wire at the battery disconnect relay. If continuity to ground on the CHX
wire at the battery disconnect relay is not present, check the continuity of the CHX wire from the battery disconnect
relay to the chassis ground. If there is good continuity to ground on the CHX wire at the battery disconnect relay, go
to step 10.
10. Check for continuity to ground on the SWS wire at the standby power relay. If continuity to ground is not present,
check the continuity of the SWS wire, diode D1, and the SWD wire to the battery disconnect relay. If the SWS/D1/
SWD wire has good continuity, go to step 11. If there is good continuity to ground on the SWS wire at the standby
power relay, go to step 12.
11. Check for continuity to ground on the CHW wire at the battery disconnect relay. If the CHW wire has good continuity
to ground, the battery disconnect relay is probably defective. If continuity to ground on the CHW wire at the battery
disconnect relay is not present, check the continuity of the CHW wire from the battery disconnect relay to the
chassis ground.
12. Check the voltage on the 2B wire at the standby power relay. If voltage is not present, the standby power relay is
probably defective. If the voltage on the 2B wire at the standby power relay is acceptable, go to step 13.
13. Check the voltage on the PC wire at Pin 10 in the MP1-C2 Connector on PCB1 in the ECM. If voltage is not present,
check the continuity of the PC circuit to junction connector JP1 and the 2B2/2B circuit to the standby power relay. If
the voltage on the PC wire is acceptable, go to step 14.
14. Check the voltage on the CMC wire at the compressor motor contactor. If voltage is not present, check the continuity
of the CMC circuit to Pin B1 in Connector MP1-C1 on PCB1 in the ECM and Fuse 5 on the ECM. If the CMC wire has
good continuity and Fuse 5 is good, the ECM may be defective. If the voltage on the CMC wire is acceptable, go to
step 15.
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