Extremely Low Refrigerant Charge in the System
Indications:
Low side pressure LOW.
High Side Pressure LOW.
Air from vents in the cab seems warm.
If there is a low pressure switch in the
system, it may have shut off the com-
pressor clutch.
Extremely low or no refrigerant in the system. There
may be a leak in the system.
Check for leaks by performing leak test.
No Leaks Found:
1. Add refrigerant to the system (at least half of the
normal full charge amount).
2. Performance test system.
Leaks Found:
1. If a leak is present at a connection, tighten the
connection, then add refrigerant as required.
2. It may be necessary to use a jumper wire to en-
able the compressor to operate, if the compres-
sor has shut down due to faulty pressure
sensing switch.
3. If a system component needs to be replaced, re-
cover all refrigerant from the system. Replace
the defective part, then check the compressor
oil level; refill compressor oil as necessary.
4. Evacuate system.
5. Charge system with new / recycled refrigerant.
6. Check A/C operation and do system
performance test.
Air and/or Moisture in the System
Indications:
Gauge Reading- Low Side Normal
High Side Normal
Air and/or Moisture in the System
Gauge Reading- Low Side Normal
High Side Normal
Cause- Air and/or moisture in the system.
The air from the vents in the cab is only slightly
cool. In a cycling type system with a thermo-
static switch, the switch may not cycle the
clutch on and off, so the low pressure gauge
will not fluctuate.
Repair Procedure:-
Test for leaks, especially around the compres-
sor shaft seal area. When the leak is found,
recover refrigerant from the system and repair
the leak. Replace the receiver-drier or accumula-
tor because the desiccant may be saturated
with moisture. Check the compressor and re-
place any refrigerant oil lost due to leakage.
Evacuate and recharge the system with refriger-
ant, then check AC operation and performance.
M9-22 Air Conditioning System M09010 6/97
for HFC 134a Refrigerant
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