Dodge RAM 1500 1998 Owner's Manual page 2493

24 - 6 HEATING & AIR CONDITIONING
HEATING & AIR CONDITIONING (Continued)
Condition
The low side pressure is too
low, and the high side
pressure is too high.
DIAGNOSIS AND TESTING - HEATER
PERFORMANCE TEST
Review Safety Warnings and Cautions before per-
forming this procedure (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - WARNING) and
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - CAUTION).
Check the coolant level, drive belt tension, vacuum
line connections, radiator air flow and fan operation.
Start engine and allow to warm up to normal tem-
perature.
WARNING: DO NOT REMOVE RADIATOR CAP
WHEN ENGINE IS HOT, PERSONAL INJURY CAN
RESULT.
If vehicle has been run recently, wait 15 minutes
before removing cap. Place a rag over the cap and
Ambient Air Temperature
Minimum Air Temperature at
Floor Outlet
Both of the heater hoses should be HOT to the
touch (coolant return hose should be slightly cooler
than the supply hose). If the coolant return hose is
much cooler than the supply hose, locate and repair
the engine coolant flow obstruction in the heater sys-
tem. If both heater hoses are cool to the touch,
inspect the engine cooling system (Refer to 7 -
COOLING - DIAGNOSIS AND TESTING).
OBSTRUCTED COOLANT FLOW Possible loca-
tions or causes of obstructed coolant flow are as fol-
lows:
• Pinched or kinked heater hoses.
• Improper heater hose routing.
• Plugged heater hoses or supply and return ports
at the cooling system connections.
• Plugged heater core.
Possible Causes
1. Restricted refrigerant flow
through the refrigerant lines.
2. Restricted refrigerant flow
through the fixed orifice tube.
3. Restricted refrigerant flow
through the condenser.
TEMPERATURE REFERENCE CHART
15.5° C
(60° F)
62.2° C
(144° F)
1. See Liquid, Suction, and Discharge Line in this
group. Inspect the refrigerant lines for kinks, tight
bends or improper routing. Correct the routing or
replace the refrigerant line, if required.
2. See A/C Orifice Tube in this group. Replace
the liquid line, if required.
3. See A/C Condenser in this group. Replace the
restricted condenser, if required.
turn it to the first safety stop. Allow pressure to
escape through the overflow tube. When the system
stabilizes, remove the cap completely.
MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system by
two heater hoses. With the engine idling at normal
operating temperature, set the temperature control
to maximum heat, the mode control to the floor posi-
tion, and the blower in the highest speed position.
Using a test thermometer, check the temperature of
the air being discharged from the floor outlets. Com-
pare the test thermometer reading to the Tempera-
ture Reference chart.
21.1° C 26.6° C
(70° F) (80° F)
63.8° C 65.5° C
(147° F) (150° F)
If proper coolant flow through the cooling system is
verified, and heater outlet air temperature is insuffi-
cient, a mechanical problem may exist.
MECHANICAL PROBLEMS Possible causes of
insufficient heat due to mechanical problems are as
follows:
• Obstructed cowl air intake.
• Obstructed heater system outlets.
• Blend door not functioning properly.
TEMPERATURE CONTROL
If the heater outlet air temperature cannot be
adjusted with the temperature control knob on the
A/C-heater control, the following could require ser-
vice:
• Blend door binding.
• Faulty blend door motor.
Correction
32.2° C
(90° F)
67.2° C
(153° F)
DR