Service Manual

627333-A 5-47
HVAC Testing and Adjusting
Labeling Procedure
Attach a cable strapped label to air conditioning system
indicating system charge.
Charging System
NOTE: An accurate refrigerant charge is only
determined by weight or temperature of
evaporator core. Pressures can not be used to
determine if air conditioning system is correctly
charged. Do not add or remove part of
refrigerant.
NOTE: Never charge liquid or gas through discharge
side (high) of system when engine is in
operation.
IMPORTANT: In an expansion valve system which uses
poly alkaline glycol (PAG), sight glass is not a
reliable way to determine system charge.
NOTE: For expansion valve systems containing PAG
oil, sight glass can not be used to charge
system. for a full system charge, refrigerant
must be recovered and evacuated. After
recovery and evacuation, charge system with
correct amount of refrigerant. This is the only
procedure recommended.
NOTE: If engine is running, charge system with
refrigerant gas through low pressure side.
Never charge liquid refrigerant through suction
side (low) of air conditioning system. If engine is
not running, charge with liquid or gas through
high pressure side.
NOTE: Before charging system, check the following
important items:
1. Condenser and evaporator
• Inspect condenser and evaporator for foreign
material such as dirt, insects, plastic bags, etc.
These things can will inhibit airflow.
• With roof-mounted condensers, verify both fan
motors are running. Check for restrictions as a
clean condenser will increase compressor life.
2. Check for a loose belt on compressor.
3. Clean fresh and recirculation filters.
4. Check moisture indicator on the receiver-dryer or
in-line dryer, replace if indicator is pink or white. A
blue moisture indicator is normal.
5. Check condensation tube on evaporator to ensure it
is not plugged and is in place.
NOTE: Before an accurate moisture reading, a new
receiver-dryer requires two to three hours of
operation.
NOTE: Preferred method for charging air conditioning
system is below:
• Recover refrigerant.
• Evacuate system.
• Charge system with correct amount of
refrigerant, measured by weight.
NOTE: After system has been recovered and
evacuated, charge with correct amount of
refrigerant measured by weight.