Service Manual

5-50 627333-A
HVAC Testing and Adjusting
ADDING ADDITIONAL REFRIGERANT TO
AN AIR CONDITIONING SYSTEM WITH
LOW CHARGE
IMPORTANT: Failure to properly follow procedure may
cause compressor failure. The following
procedure is NOT the preferred method for
charging an air conditioning system, the
preferred method of measuring refrigerant is by
weight.
IMPORTANT: If system has no refrigerant, evacuate
system before charging. Refrigerant charge
should be measured by weight.
NOTE: The following is only applicable if the inlet air
temperature at condenser is between 21 °C
(70.0 °F) and 32 °C (90.0 °F) and may be
repeated a second time to achieve proper
charge method.
1. Connect manifold gauge set to discharge and
service ports on compressor.
2. Ensure low and high pressure valves are closed on
the manifold gauge set.
3. Turn valve on tank counterclockwise to release
refrigerant to charging hose.
NOTE: Ensure cylinder of refrigerant is upright to allow
refrigerant to enter system as a gas.
4. Loosen hose connection on charging hose at
manifold gauge set for two to three seconds, then
tighten connection. This action allows air to be
released from charging hose.
5. Start engine and operate at 1000 rpm.
6. Move temperature control knob to MAXIMUM cool
and move fan switch to HIGH.
NOTE: Recovering refrigerant and evacuating system
is preferred method for charging air conditioning
system. After system has been recovered and
system has been evacuated, system needs to
be charged with the correct amount of
refrigerant measured by weight.
7. Open low pressure valve on manifold gauge set to
release refrigerant into low pressure hose, this
connects to suction service valve on the
compressor. Check pressure gauge and note gauge
reading, should not exceed normal operating ranges
during procedure. Slowly add refrigerant until
accumulator is cool. Temperature of vents inside
cab should decrease during procedure.
8. After accumulator becomes cool, add 0.34 kg
(0.750 lb) of refrigerant to system for reserve,
measure by weight.
9. To prevent additional flow of refrigerant into
compressor, close low pressure valve. Allow system
to stabilize for five minutes, the inlet and outlet on
accumulator should be cool.
NOTE: If low pressure valve is opened completely,
reading will appear excessively high until
system becomes fully charged.
10. Gauge reading for low pressure valve should be
within normal range after system is charged. Gauge
reading for high pressure valve should be within
normal range after charging system. If gauge
readings are within normal range, go to Step 11, if
not go to Step 12.
11. If pressure on suction side or discharge pressure
becomes too high, system is overcharged.
Completely close valve on refrigerant tank to shut off
flow of refrigerant to charging hose. Shut off engine,
recover charge and evacuate system and recharge
system to correct charge.
12. Move air conditioning controls to OFF and stop
engine.
13. Remove manifold gauge set.
MANIFOLD GAUGE SET (REFRIGERANT)
- REMOVE
Remove charging hoses properly to prevent a low
system charge. For accurate refrigerant charge, remove
refrigerant from charging hoses referring to the following:
1. Allow compressor to continue operating. Close
valve on high pressure side, located near charging
ports. Disconnect high pressure hose from air
conditioning system.
2. Open high and low pressure valves at gauge set.
Refrigerant in hoses will be removed by compressor
through low pressure hose.
3. Close valve on low pressure side, located near the
charging ports. Disconnect low pressure hose from
air conditioning system and system is now charged.
NOTE: After manifold gauge set is removed, cap
charging valves.