Service Manual

5-36 627333-A
HVAC Testing and Adjusting
GENERAL TROUBLESHOOTING
INFORMATION
• Low refrigerant charge causes losses of cooling and
lubrication in compressor, results in failed
compressor.
• Overcharge of refrigerant causes a loss of cooling
ability. An overcharged system contains excess
liquid refrigerant that can severely damage
compressor. An overcharged system fails at a rate
of twice an undercharged compressor.
• Too much oil in system contributes to a low
refrigerant charge.
• A small amount of moisture will penetrate the hoses
used in R134a systems. Change accumulator,
desiccant, and filter annually. Moisture causes
sludge resulting in a plugged system and can also
cause the formation of ice at the orifice of the tube
assembly.
• When outside temperature is above 32 degrees C
(90 degrees F) or if the humidity is high, gauge
readings for an undercharged R134a system
appear as symptoms of overcharge. Incorrect
gauge readings lead to a loss of cooling ability and
compressor failure.
• Removed refrigerant cannot be weighed accurately.
A 20 to 30 percent error can occur as a result of
inaccuracies of devices used for recovery.
• Check scale for accuracy after every 30 days or
every 30 uses.
• If system pressure rises above 0 kPa (0 PSI) within
five minutes of recovering a system, recover again
until pressure does not increase. Recovering
system again empties accumulator of refrigerant.
• Presence of frost on accumulator is normal, the
thickness of frost depends on outside temperature
and humidity.
• Perform regular maintenance on refrigerant service
units and change vacuum pump oil.
• Secure lines and wires to prevent damage.
• The formation of black sludge deposits in the
system is caused by moisture in R134a systems
and by mixing charges of R134a and R12.
• The presence of white foam during recovery is
normal, it is caused by mixing oil and refrigerant.
• R134a system charges must be within 0.03 kg (1oz)
to .06 kg (2oz) of specified charge for unit.
A loss of cooling ability or failure of compressor may be
caused by one or more of the following conditions.
• Low charge
• Overcharge
• Too much oil
• Dirty or plugged filter
• Dirty or plugged condenser
• Dirty or plugged evaporator
• Dirty or plugged orifice tube
VISUAL INSPECTION
Before a performance check of the air conditioning
system, check the following:
1. Check condenser and evaporator.
a. Check for any restriction obstructing air flow
such as dirt, insects, plastic bags, etc.
2. Clean fresh air and recirculation filters.
3. Check for a loose belt on compressor.
4. Check drain tube on evaporator for obstruction.
5. Start unit and set air conditioner on HIGH. Place
hand on accumulator, a properly charged system
should feel cool or cold to the touch.