Dodge RAM TRUCK 1500 1995 Service Manual page 1678

BR
HEATING AND AIR CONDITIONING 24 - 9
A S R C O N D I T I O N I N G A N D
HEATER PERFORMANCE TEST
INDEX
page
A/C Performance Test 9
A/C PERFORMANCE TEST
The air conditioning system is designed to provide
the passenger compartment with low temperature
and low humidity air. The evaporator, located in the
heater-A/C housing behind the instrument panel, is
cooled to temperatures near the freezing point. As
warm damp air passes over the fins in the evapora­
tor, the air is cooled and moisture is removed to con­
dense on the fins. During periods of high heat and
humidity an A/C system will be more effective in the
RECIRC mode. With the control set to REC1RC, only
air from the passenger compartment passes through
the evaporator. As the passenger compartment air
dehumidifies, A/C performance levels improve.
Review Safety Precautions and Warnings before
proceeding with this procedure. Air temperature in
test room and in the vehicle must be 21°C (70°F)
minimum for this test.
(1) Connect an engine tachometer and manifold
gauge set.
(2) Set control to A/C, RECIRC (PANEL) tempera-
ture knob on full cool and Mower on HIGH (Compres­
sor ON).
(3) Start engine and hold at 1,000 RPM with A/C
clutch engaged.
(4) Engine should be warmed up with windows
and/or doors opened.
(5) Insert a thermometer in the left center A/C out­
let and operate the engine for 5 minutes.
(6) The A/C clutch may cycle depending on ambi­
ent conditions. If clutch cycles, remove the clutch cy­
cling pressure switch connector from the switch
located on the accumulator (Fig. 1). Place a jumper
wire across the terminals of the clutch cycling pres­
sure switch connector.
(7) With the A/C clutch engaged, record the dis­
charge air temperature and the compressor discharge
pressure and. evaporator inlet pressure.
(8) Compare the discharge air temperature to the
A/C Performance (Temperature and Pressure) Chart.
If the discharge air temperature is high, refer to the
Refrigerant Service Procedures (Refrigerant Leak
Testing and Refrigerant System Diagnosis Chart.
(9) Compare the compressor discharge and suction
(evaporator inlet) pressures to the A/C Performance
(Temperature and Pressure) Chart. If the compressor
discharge pressure or suction (evaporator inlet) pres-
page
Heater Output Test . . . . . . . . . . . . . . . . . . . . . . . . . 9
Fig. 1 dutch Cycling Pressure Switch
sure is not normal, check the operation of the refrig­
erant system, referring to Refrigerant Pressure
Diagnosis Chart.
HEATER OUTPUT TEST
PRE-DIAGNOSTIC PREPARATIONS
Review Safety Precautions and Warnings before
performing the following procedures.
Check the radiator coolant level, drive belt tension
and engine vacuum line connections. Also check radi­
ator air flow and radiator fan operation. Start engine
and allow to warm up to normal operating tempera­
ture.
WARNING: DO NOT REMOVE RADIATOR CAP
W H E N ENGINE IS HOT, P E R S O N A L INJURY CAN
RESULT.
If vehicle has been run recently, wait 15 minutes
before removing cap. Place a rag over the cap and
turn it to the first safety stop. Allow pressure to es­
cape through the overflow tube. When the system
stabilizes, remove the cap completely.
MAXIMUM NEATER OUTPUT
Engine coolant is provided to the heater system by
2 heater hoses. With engine idling at normal running
temperature, set the control to maximum heat, floor
and high blower setting. Using a test thermometer,