Paccar SM001-300, Руководство по обслуживанию, Страница: 14 / 39

Page 14 of 39
Number SM001-300
HVAC: Idle Management System
Unit runs—but does not
blow cold air. 1. Airflow blockage.
2. Compressor.
3. Fuse or Relay.
4. System and Com-
pressor controller
connections/ defec-
tive compressor.
5. Condenser fan and
high pressure switch.
6. Evaporator dis-
charge temp sen-
sor/Freeze switch
defective.
7. Compressor thermal
switch.
8. Evaporator blower/
Linear Power Module.
9. Loss of charge (refrig-
erant system is ser-
viceable).
1. Clear any blockage from recirculation grill or louvers.
Also check condenser inlet and outlet for restriction (out-
side truck).
2. Check F4 compressor fuse and R3 compressor relay.
See “ C. Relay Testing ” on page 18 and “ E. Check Conti-
nuity Across Fuse Body ” on page 19.
3. Confirm all wire harness plugs are connected. Test sys-
tem and compressor controller. See “ H. Main Control-
ler/Compressor Controller ” on page 19.
4. Check high pressure switch and condenser fan. “ D.
Pressure Switch Testing ” on page 18 and “ I. Condenser
Fan Motor Testing ” on page 20.
5. Check sensor. See “ F. Discharge Temperature Sen-
sor/Freeze Switch Testing ” on page 19.
6. Check normally closed thermal switch. See “ G. Com-
pressor Thermal Limit Switch ” on page 19.
7. Check evaporator blower and linear power module. See
“ J. Evaporator Blower Motor and Linear Power Module
Testing ” on page 20.
8. If all tests check OK, a loss of refrigerant charge may
have occurred.
Unit cycles On and Off and
doesn’t cool 1. Poor electrical con-
nection.
2. Condenser fan inop-
erative.
3. Air flow blockage
causing high pres-
sure or freeze condi-
tion.
1. Check all electrical connections.
2. Check condenser fan. See “ I. Condenser Fan Motor
Testing ” on page 20.
3. Check for restricted airflow outside truck at condenser
inlet and outlet and at louvers and recirculation grill.
Check pressure switch, thermal limit and/or discharge
temperature sensor. See “
D. Pressure Switch Testing ”
on page 18 , “ F. Discharge Temperature Sensor/Freeze
Switch Testing ” on page 19, and “ G. Compressor Ther-
mal Limit Switch ” on page 19.
Unit blows cold air—but
low airflow 1. Check all duct work
connections.
2. Air flow restricted.
3. Evaporator Blower
motor inoperative.
1. Make sure all ducts are connected, sealed and secure.
2. Check for airflow at louvers and recirculation grill.
3. Check evaporator blower motor and linear power mod-
ule. See “ J. Evaporator Blower Motor and Linear Power
Module Testing ” on page 20.
Table 1. A/C System Diagnostic
PROBLEM POSSIBLE CAUSE CORRECTIVE ACTION
/
“Appendix” on page 18.