Section II.1. TROUBLESHOOTING AND TESTING THE AIR
Before testing the operation of the air conditioning
system, make the following checks:
Make sure the refrigerant compressor's drive belt
is not damaged and is correctly tensioned. Also
check the compressor mountings for tightness.
Check for broken, burst, or cut hoses; also check
for loose fittings on all parts.
Check for road debris build-up on the condenser
coil fins. Using air pressure and a whiskbroom or
a soapy spray of water, carefully clean off the
condenser; be careful not to bend the fins.
Check the color of the moisture indicator sight
glass. If the color is a deep cobalt blue, the
refrigerant charge is dry. If the indicator is not
blue, the system is contaminated with moisture.
Notify your supervisor.
If there is not enough airflow, make sure that
leaves or other debris has not entered the fresh air
ports under the windshield. If debris has entered,
it could clog the fins of the evaporator core, and
Also, be sure that all ducts are connected to the
dash louvers and that the air-control flaps in the
heater housing are moving properly (this requires
removal of the right and center dash panel).
Following is a brief description of symptoms or
conditions that could exist if something goes wrong with
a refrigerant part.
The receiver-drier is normally at outside temperature.
To the touch, the entire length of the unit should be the
same temperature. If noticeable cool spots exist, notify
A blockage at the inlet of the unit will cause high head
pressures; outlet blockages will cause low head
pressures and little or no cooling.
If the moisture indicator is pink or white (showing that the
system is wet), the receiver-drier is saturated with
moisture and must be replaced. Notify your supervisor.
Although they are not physically connected, there is a
close tie between a vehicle's air conditioner and its
cooling system. Poor air conditioner cooling can be the
result of a problem in the cooling system.
If the cooling system does not work correctly, the heat of
the engine will rise to abnormal levels. The added heat
will transfer to the air conditioner, other underhood parts,
and maybe make its way into the cab. The added heat
makes it necessary for the air conditioner to work harder
and, at the same time, it reduces the air conditioner's
ability to cool down the air in the cab. Also, if the water
regulating valve isn't closing all the way, heat will enter
the cab, giving the impression that the air conditioning
system is not working.
Problems that start in the expansion valve show up as
follows: when stuck closed, the evaporator coil and the
expansion valve will be at outside temperature; when
stuck open, both the coil and the valve will be extremely
cold with frost or ice build-up.
Because the expansion valve channels are very small,
blockages in the system tend to be found here (the valve
is very sensitive to contamination). Usually, the
contaminant is water; less than a drop of water is all it
takes to make the valve inoperative. When water
reaches the valve, the extreme cold that results from the
pressure drop freezes the water, forming a block of ice in
the valve. After the system shuts down and the valve
warms up, the ice melts, and the valve operates again,
only to freeze up when the moisture returns.
Change 3 3-92.1