GMC 1986 P-Truck Service Manual page 75

1B-12 AIR CONDITIONING
THE FOLLOWING PROCEDURES SHOULD BE APPLIED BEFORE PERFORMANCE TESTING AN A/C SYSTEM.
CHECK FOR PROPER BELT INSTALLATION AND TENSION
WITH J-23600
CHECK FOR PROPER CLUTCH COIL TERMINAL
CONNECTOR INSTALLATION.
CHECK FOR CLUTCH AIR GAP (0.022-0.057) (.56-1.45
mm).
CHECK FOR BROKEN, BURST, OR CUT HOSES. ALSO
CHECK FOR LOOSE FITTINGS ON ALL COMPONENTS.
CHECK FOR CONDENSOR AIR BLOCKAGE DUE TO
FOREIGN MATERIAL.
NORMAL AIR FLOW
CHECK DISCHARGE AIR TEMPERATURE
SEE FIGURE 8.
DISCHARGE TEMPERATURE
AT OUTLET COLD
CHECK FOR AIR LEAKS THROUGH DASH PANEL, DOORS,
WINDOWS, OR FROM HEATER.
CHECK FOR BLOW FUSE, INOPERATIVE BLOWER SWITCH,
BROKEN WIRE, LOOSE CONNECTIONS, LOOSE BLOWER
MOTOR GROUND WIRE OR INOPERATIVE BLOWER MOTOR.
INSUFFICIENT COOLING DIAGNOSIS CHART
D A S H M O U N T E D U N IT (M O TO R H O M E C H AS SIS U N ITS )
CHECK AIR FLOW
BLOWER NOT OPERATING - CHECK BLOWER OPERATION -
HIGH OUTLET AIR
TEMPERATURE
CHECK SIGHT GLASS
REFER TO FIGURE 14
NORMAL EVAPORATOR
SYSTEM HAS EXCESS MOISTURE. REPLACE
RECEIVER DEHYDRATOR AND EVACUATE
THOROUGHLY. RECHARGE SYSTEM
Figure 13—Insufficient Cooling Diagnosis Chart
6. CHECK FOR PROPER AIR DUCTING HOSE CONNECTIONS.
7. CHECK HEATER TEMPERATURE DOOR ADJUSTMENT,
ADJUST IF INCORRECT.
8. CHECK EVAPORATOR SEALING FOR AIR LEAK, REPAIR IF
LEAKING.
9 INSTALL PRESSURE GAGES AND THERMOMETER AND
MAKE PERFORMANCE TEST.
NO OR LOW AIR FLOW
CHECK FOR LOOSE OR DISCONNECTED AIR
DISTRIBUTION DUCTS, RESTRICTED OR LEAKING
AIR DUCTS, PARTIALLY CLOSED AIR OUTLET
VALVE OR CLOGGED EVAPORATOR CORE, IF
ABOVE CHECK IS OK, CHECK FOR ICE BLOCKING
EVAPORATOR.
CHECK FOR LOW EVAPORATOR PRESSURE
1. ALLOW SYSTEM TO W ARM UP.
2 STOP AND RESTART ENGINE
3 CHECK EVAPORATOR PRESSURE
IMMEDIATELY AFTER RESTART AND PULL
DOWN OF EVAPORATOR PRESSURE.
PRESSURE
NORMAL BLOWER OPERATION
ICE BLOCKING
EVAPORATOR
LOW EVAPORATOR PRESSURE
CHECK FOR MALFUNCTIONING
EXPANSION VALVE. REFER
TO FIGURES 11 AND 12.
F-00164