SECTION 22: HEATING AND AIR CONDITIONING
PA1621 Maintenance Manual All Series | Section Revised November 2017
45
Problem/Symptom Probable Causes Actions
Evaporator fan not
functioning
Circuit breaker CB3 (CB6 on X3
VIP) tripped
Module A54 is not powered or is
faulty
1. Check / reset circuit breaker CB3 (CB6 on
X3 VIP)
2. Check the Diagnostics menu of Driver
Information Display (DID). Select Fault
Diagnostics and Electrical System. The
message “No Response ModA54, Active”
indicates a power problem on the module.
(A CAN network problem would show the
same message but doesn't produce this
symptom).
3. Check / reset circuit breaker CB5
except:
X3 VIP check CB7
4. Check fuse F67
5. Probe gray connector on module to see if
it is powered.
6. Check / replace condenser power relay
R12 (probe R12 coil power circuit 67,
should be 24 volts).
5.7.1 Air Conditioning
TROUBLE CAUSE
Low suction pressure and frosting at dryer outlet. Clogged filter.
Low Oil Level. Check for oil leaks and for leaking oil seal. Do not
attempt to check oil level unless system has been
stabilized at least 20 minutes. See oil level
verification.
Excessively cold suction line
And
High superheat
Loss of contact between the expansion valve
bulb and the suction line or sticking of the
expansion valve.
Improper insulation.
Check for corrosion and clean, repair or replace
the valve.
Noisy or knocking compressor. Check for broken internal parts. Overhaul if
required.
Compressor vibrates excessively. Check and tighten compressor mounting bolts
and belt tension.
Low refrigerant level Check for refrigerant leaks and add refrigerant as
required.
Suction pressure rises fast after shutdown. Check compressor valve for breakage or
damage.
Insufficient air flow. Dirty or iced evaporator. Dirty air filter. Blowers
inactive. Clogged ducts.
No flow of refrigerant through expansion valve. Filter-dryer is clogged. Remote bulb has lost
charge or expansion valve is defective.
Expansion valve hisses. Bubbles in moisture and
liquid indicator.
Gas in liquid line. Add refrigerant.
Loss of capacity Clogged filter. Obstructed or defective expansion
valve.
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