freightliner FL50 1998 - Air Conditioner Checking

83–01 Air Conditioner
Checking, R–12 and
R–134a Refrigerant
Systems
Preliminary Checks
1. Apply the parking brakes and chock the tires.
2. Make sure the refrigerant compressor drive belt
is not damaged, and is correctly tensioned. Also
check the tightness of the compressor mounting
fasteners. For instructions and torque values,
see Group 01 of the Business Class
®
Trucks
Service Manual
.
3. Using a feeler gauge, check for correct clutch
clearance. For instructions, see Group 83 in the
Business Class
®
Trucks Service Manual .
4. Inspect the compressor clutch coil wire. Check
the connector for damage or looseness. Replace
the wire if it is damaged.
5. Check for broken, burst, or cut hoses. Also check
for loose fittings on all parts.
WARNING
Wear eye protection when using compressed air
or high-pressure water to clean parts, as perma-
nent harm to eyes could result from flying debris.
6. Check for a build-up of road debris on the con-
denser fins. Using a whiskbroom and air pres-
sure, or a spray of soapy water, carefully clean
off the condenser; be careful not to bend the fins.
Cooling Checking
1. Start the engine, and set engine speed at 1500
rpm. Close the doors and windows.
IMPORTANT: When outside temperature and
humidity are high, it will take longer to cool the
cab, especially if fresh-air vents are left open.
2. Turn on the air conditioner; set the controls at
maximum cooling and blower speed.
3. Allow the system to run for at least 10 minutes
(longer on hot and humid days).
4. Check air flow from the vents. If there is not
enough air flow, check the air intake vent for
blockage, and the blower motor for proper opera-
tion.
If the air flow is not cold enough, see Group 83
of the
Business Class
®
Trucks Service Manual .
5. Carefully feel the system lines.
• The compressor discharge line should feel
hot.
• The condenser inlet line should be notice-
ably warmer than the outlet line.
• The line from the condenser should feel
warm.
• The inlet and outlet lines of the receiver-
drier should be about the same tempera-
ture.
• The line from the receiver-drier to the
evaporator should feel warm.
• The line from the evaporator to the com-
pressor should feel cold.
NOTE: Oily spots on the lines or at the fittings
could indicate a system leak.
Refrigerant Checking
1. If equipped with a moisture indicator sight glass,
check the color of the moisture indicator. See
Fig. 1, Ref. 1.
If the indicator is a deep cobalt blue, the refriger-
ant charge is dry.
If the indicator is
not blue, the system is contami-
nated with water; recover the refrigerant, replace
the receiver-drier, evacuate the system, and add
a full refrigerant charge.
2.
On R–12 refrigerant systems only , check the
receiver-drier sight glass. See Fig. 1, Ref. 2.
The presence or absence of bubbles tells
whether or not the system has enough refriger-
ant. Bubbles normally appear when the system is
started, then disappear after a few seconds. Only
an occasional bubble should be seen during nor-
mal operation. If bubbles continue all of the time
the system is running, the system is merely low
on (not completely out of) refrigerant.
Heater and Air Conditioner 83
Business Class Trucks Maintenance Manual, January 1998 83/1