1991 MITSUBISHI MONTERO Service Manual

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A/C -H EA TE R S YSTE M - M AN UAL

1991 M it s u bis h i M onte ro
1991 MANUAL A/C-HEATER SYSTEMS
Chrysler Motors, Mitsubishi
Chrysler Motors: Colt Vista, Ram-50
Mitsubishi: Montero, Pickup
* PLEASE READ THIS FIRST *
CAUTION: When discharging air conditioning system, use only approved
refrigerant recovery/recycling equipment. Make every attempt
to avoid discharging refrigerant into the atmosphere.
A/C SYSTEM SPECIFICATIONS
SPECIFICATIONS TABLE








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Compressor Type
Colt Vista & Montero .................... Nippondenso 10-Cyl.
Pickup & Ram-50 ............................... Sanden Scroll
Compressor Belt Deflection
Colt Vista ............................ 11/32-7/16" (8-11 mm)
Montero ............................. 21/64-3/8" (8.5-9.5 mm)
Pickup & Ram-50 .................... 21/64-25/64" (8.5-10 mm)
Compressor Oil Capacity
Colt Vista & Montero ............................... 2.7 ozs.
Pickup & Ram-50 .................................... 5.0 ozs.
Refrigerant (R-12) Capacity
Colt Vista & Montero ................................ 32 ozs.
Pickup & Ram-50 ..................................... 30 ozs.
System Operating Pressures (1)
Colt Vista, Pickup & Ram-50
High Side .................... 130-220 psi (9.1-15.5 kg/cm
)
Low Side ........................ 20-26 psi (1.4-1.8 kg/cm)
Montero
Dual Unit
High Side .................. 142-199 psi (9.9-14.0 kg/cm
)
Low Side ...................... 16-30 psi (1.1-2.1 kg/cm)
Single Unit
High Side ................... 102-142 psi (7.1-9.9 kg/cm
)
Low Side ...................... 18-32 psi (1.3-2.2 kg/cm)
(1) - With ambient temperature at least 80
F (27C).








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DESCRIPTION
Slight variations exist among the manual A/C-heater systems
used. Either Sanden Scroll or Nippondenso 10-cylinder compressor is
used. Cycling of the compressor clutch is controlled by switches which
monitor temperatures and pressures.
Compressors will only operate within the normal operating
temperatures and pressures set for each model. An electric condenser
fan operates whenever A/C system is operating. System components used
vary depending upon model. Most systems include an A/C compressor
control unit, fan switch, evaporator, temperature sensor, high and low
(or dual) pressure switch, engine coolant temperature switch,
compressor, condenser, receiver-drier and various pipes and hoses.

OPERATION
A/C SWITCH
The A/C switch is located in the lower, center section of
control panel. See Fig. 1. When switch is pushed, air conditioning
will operate if blower motor control lever is in a position other than
OFF.
When activated, the A/C button/switch allows the A/C
compressor clutch to engage and operate the compressor. On some
models, a light on the button will glow when button/switch is
activated.
Fig. 1: A/C Switch & Control Panel
Courtesy of Mitsubishi Motor Sales of America.
AIR SELECTOR LEVER
The air selector lever is located in the upper, left corner
of control panel and moves horizontally to select the source of air
needed inside of passenger compartment. Lever moves from OFF position
on the left to the outside air mode, to the mixture of both outside
and inside air mode, and to the recirculation mode on the right. Lever
should normally be set in the recirculation mode for maximum A/C
cooling.
BLOWER MOTOR CONTROL LEVER
Blower motor control lever is located on the lower, left
corner of control panel and moves horizontally to select blower motor
speeds. As lever is moved from far left or OFF position, increasing

speeds of blower operation are selected. In order for A/C system to
operate, blower motor control lever MUST be in a position other than
OFF.
MODE SELECTOR LEVER
Mode selector lever is located in upper right corner of
control panel. Either 2 or 6 modes are available to achieve desired
distribution of air from various outlets.
On all models, air is directed to windshield and side
windows and comes out from the panel outlets when mode selector lever
is positioned to the far left. When lever is moved one detent to the
right, air is directed to windshield and side windows simultaneously.
On 6-mode models, air is directed to floor area, windshield,
and side windows when lever is moved 2 detents to the right. When
lever is moved 3 detents to the right, air is directed to floor area.
When lever is moved to the second to last detent on control panel, air
is directed to floor area and panel outlets. When lever is in the far
right position, air will be directed to panel outlets only.
TEMPERATURE CONTROL LEVER
The temperature control lever operates blend-air door in the
heater/air conditioning unit, mixing cooled and heated air so the
selected air temperature can be obtained. The system will provide
cooled air when A/C switch is in ON position and blower motor is in
any position other than OFF. The temperature control lever should be
in the far left (maximum cooling) side of temperature selection scale
when maximum A/C cooling is desired.
DUAL PRESSURE SWITCH
The dual pressure switch, located in the refrigerant line
near condenser, is wired in series with compressor clutch. Whenever
system pressures drop below or increase above the control point of the
switch, power supplied to compressor will be cut and compressor
activity will cease until pressures are back to within operating
ranges.
ENGINE COOLANT TEMPERATURE SWITCH
The engine coolant temperature switch, located on thermostat
housing, is wired in series with compressor clutch. When coolant
temperature is greater than switch control temperature, power to
compressor is cut and compressor is turned off until temperature
returns to operating range.
EVAPORATOR THERMISTOR
The evaporator thermistor, attached to evaporator fins, is
wired in series with compressor clutch and prevents evaporator
freezing. Power to compressor clutch is cut if control temperature is
exceeded, allowing evaporator to thaw. When temperature returns to
operating range, thermistor allows power to compressor clutch.
FUSIBLE PLUG
A fusible plug, located on receiver-drier, melts and allows
refrigerant to escape when ambient temperatures in engine compartment
reach 221
F (105C). Once fusible plug has blown, it cannot be reused
and must be replaced.

HIGH PRESSURE SWITCH
The high pressure switch, installed in refrigerant line, is
wired in series with compressor clutch. When refrigerant pressures
rise above switch control pressure point, power to compressor clutch
is cut. The high pressure switch may also be activated when airflow
through condenser is blocked or when system is overcharged.
HIGH/LOW PRESSURE CUT-OFF SWITCH
The High/Low Pressure Cut-Off (HLPCO) switch, located on
refrigerant line, is wired in series with compressor clutch. Switch
cuts off power to compressor clutch when refrigerant pressures are
above or below switch control point. When pressure returns to normal
operating range, compressor clutch operation resumes.
LOW PRESSURE SWITCH
The low pressure switch, located in receiver-drier, is wired
in series with compressor clutch. When refrigerant pressure drops
below switch control point (usually due to leak in system), power to
compressor clutch is cut.
REFRIGERANT TEMPERATURE SWITCH
The refrigerant temperature switch, located on rear of
compressor, detects refrigerant temperature discharged from
compressor. A/C Control Unit (ACCU) uses this information to control
compressor clutch cycling.
ADJUSTMENTS
NOTE: For adjustment procedures not covered in this article, see
appropriate HEATER SYSTEM article in the AIR CONDITIONING &
HEAT Section.
MODE CONTROL CABLE
Montero
Move mode selector lever to far left (DEF) position. Move
mode door lever upward in direction indicated by arrow. See Fig. 2.
Connect inner wire to lever, and secure outer housing using clip.
Operate mode control knob to ensure proper operation.
Fig. 2: Adjusting Mode Selection Cable (Montero)
Courtesy of Mitsubishi Motor Sales of America.
TEMPERATURE CONTROL CABLE

Montero
1) Move temperature selector lever to far left position.
Remove heater control valve cover. Disconnect heater control valve
wire from blend door lever. Push heater control valve inward (closed).\
2) Move blend door lever downward in direction indicated by
arrow. See Fig. 3. Connect inner wire to lever, and secure outer
housing using clip. Adjust heater control valve wire so valve is fully
closed. Operate mode control knob to ensure proper operation.
Reinstall heater control valve cover.
Fig. 3: Adjusting Temperature Selection Cable (Montero)
Courtesy of Mitsubishi Motor Sales of America.
TROUBLE SHOOTING
AIR NOT COOL
1) Ensure compressor clutch is operating. If compressor
clutch is not operating, check fuses and relay. Check A/C switch.
Check high and low pressure switches or dual pressure switch. Check
thermistor, thermo relay or Electronic Cycling Clutch Switch (ECCS).

Check blower switch and relay. Check A/C compressor clutch coil.
2) Ensure system is properly charged with correct amount of
refrigerant. Add refrigerant or evacuate and recharge system as
necessary. Ensure receiver-drier is not clogged. Check compressor belt
for proper tension. Check for clogged expansion valve. Check
compressor operation. Repair or replace compressor as necessary.
INSUFFICIENT AIRFLOW
Check for air leakage at air duct joint. Check for frost on
evaporator. Ensure blower motor is operating properly. Check for
obstructed air intake.
INSUFFICIENT COOLING
Ensure system is properly charged with correct amount of
refrigerant and free of air and moisture. Add refrigerant or evacuate
and recharge system as necessary. Ensure receiver-drier is not
clogged. Ensure sufficient airflow through condenser exists. Check
compressor belt for proper tension. Check compressor operation. Repair
or replace compressor as necessary. Check for clogged expansion valve.
Replace expansion valve as necessary.
INTERMITTENT COOL AIR
Check for air or moisture in system. Evacuate and recharge
system as necessary. Check for expansion valve malfunction. Replace
expansion valve if necessary. Check compressor belt for proper
tension.
TESTING
A/C SWITCH
1) Disconnect A/C switch harness connector. Using appropriate
wiring diagram as a guide, jumper appropriate terminals of A/C switch
wiring harness connector. See Fig. 4.
2) Turn blower on and momentarily turn ignition on without
starting engine. Listen for compressor clutch engagement. If
compressor clutch does not engage, check fuse and other components
wired in series with compressor clutch.
Fig. 4: A/C Switch Connector ID
Courtesy of Mitsubishi Motor Sales of America.
AIR THERMO & AIR INLET SENSORS

1) Disconnect sensor connector at evaporator case. Using an
ohmmeter, measure continuity between sensor terminals. See AIR THERMO
& AIR INLET SENSORS SPECIFICATIONS table.
2) If resistance is not within specifications, sensor is
faulty and must be replaced. If resistance is within specifications
and all other components are okay, replace A/C compressor control unit
(if equipped).
AIR THERMO & AIR INLET SENSORS SPECIFICATIONS TABLE









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Sensor Temperature Ohms
Air Thermo Sensor
32
F (0C) .................................. 11,400
50F (10C) ................................... 7320
68F (20C) ................................... 4860
86F (30C) ................................... 3310
104F (40C) .................................. 2320
Air Inlet Sensor
32
F (0C) .................................... 3310
50F (10C) ................................... 2000
68F (20C) ................................... 1250
86F (30C) .................................... 810
104F (40C) .................................... 530








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BLOWER RESISTOR
Disconnect blower resistor connector. Using an ohmmeter,
measure resistance between terminals indicated in BLOWER RESISTOR
RESISTANCE table. See Fig. 5.
BLOWER RESISTOR RESISTANCE TABLE









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Terminal Ohms
Colt Vista
1 & 2 ................................ Approx. 1.22
1 & 3 ................................ Approx. 0.41
1 & 4 ................................ Approx. 2.65
1 & 5 ................................... Approx. 0
Montero (Front)
1 & 2 ................................ Approx. 1.22
1 & 3 ................................ Approx. 0.41
1 & 4 ................................ Approx. 2.25
1 & 5 ................................... Approx. 0
Montero (Rear)
2 & 4 ................................. Approx. 0.5
1 & 4 ................................. Approx. 1.8
3 & 4 ................................. Approx. 3.3
Pickup & Ram-50
1 & 2 ................................ Approx. 1.19
1 & 3 ................................ Approx. 0.50
1 & 4 ................................ Approx. 2.33
1 & 5 ................................... Approx. 0









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Fig. 5: Testing Blower Resistor
Courtesy of Mitsubishi Motor Sales of America.
BLOWER SWITCH
With blower switch in position indicated in BLOWER SWITCH
CONTINUITY TEST table, ensure continuity exists between terminals
listed. See Fig. 6 or 7.
BLOWER SWITCH CONTINUITY TEST TABLE