1991 MITSUBISHI MONTERO heater

* Wrap shop towels around fuel return and high pressure hoses
to prevent fuel splashing on engine. Disconnect fuel return
hose and high pressure fuel hose to drain any residual fuel.
ENGINE
Removal (Montero & Pickup)
1) Remove hood. Drain cooling system, and remove radiator.
Remove skid plate and splash shields. Release fuel system pressure.
See FUEL PRESSURE RELEASE under REMOVAL & INSTALLATION. Disconnect
negative battery cable.
2) Remove air cleaner ducts. Remove accessory drive belts.
Remove and support A/C compressor and power steering pump. DO NOT
disconnect hoses from compressor or pump. Disconnect oil cooler hoses.
Cover fuel hose using shop towel, and disconnect high pressure fuel
hose and "O" ring. Remove fuel return hose.
3) Label and disconnect all vacuum hoses. Disconnect cooling
system hoses. Label and disconnect all electrical connections from
engine. Remove heat shield from motor mounts. Remove motor mount
bolts. Ensure all hoses and wires are disconnected and set aside.
4) Disconnect exhaust pipe from exhaust manifolds. Remove
starter. Attach engine hoist to engine. Support transmission.
Disconnect engine from transmission. See appropriate article in
CLUTCHES or TRANSMISSION SERVICING. Remove engine.
Installation (Montero & Pickup)
To install, reverse removal procedure. Install new "O" ring
on fuel line. Install new exhaust gaskets and nuts. See TORQUE
SPECIFICATIONS (MONTERO & PICKUP) table at end of article. Adjust
fluid levels.
Removal (3000GT)
1) Release fuel pressure. See FUEL PRESSURE RELEASE under
REMOVAL & INSTALLATION. Remove hood. Remove cruise control vacuum pump
and linkage. On turbo models, remove necessary turbo air intake hoses
and pipes. On all other models, remove air cleaner hoses.
2) On all models, drain cooling system. Drain engine oil and
transaxle oil. Remove heater hoses and radiator hoses. Remove
transaxle assembly. See appropriate article in CLUTCHES or
TRANSMISSION SERVICING.
3) Remove radiator. Label and disconnect all vacuum hoses.
Label and disconnect all electrical connections and harnesses from
engine. Remove accessory drive belts.
4) Remove and support A/C compressor and power steering pump.
DO NOT disconnect hoses from compressor or pump. Cover fuel hose using
shop towel, and disconnect high pressure fuel hose and "O" ring.
Remove fuel return hose.
5) On turbo models, disconnect oil cooler and vacuum hoses.
On all models, remove motor mount bolts and brackets. Ensure all hoses
and wires are disconnected and set aside. Attach engine hoist to
engine. Remove engine.
Installation
To install, reverse removal procedure. Install new "O" ring
on fuel line. Install new exhaust gaskets and nuts. See TORQUE
SPECIFICATIONS (3000GT) table at end of article. Adjust fluid levels.
UPPER INTAKE MANIFOLD
Removal (Montero & Pickup)
1) Remove air intake hose. See Fig. 1. Remove accelerator
cable adjusting bolts. On models equipped with automatic transmission,
remove throttle control cable. On all models, remove accelerator

released before disconnecting fuel lines.
Removal
1) Release fuel pressure. See FUEL PRESSURE RELEASE under
REMOVAL & INSTALLATION. Remove upper intake manifold. See UPPER INTAKE
MANIFOLD under REMOVAL & INSTALLATION.
2) Drain cooling system. Remove high pressure and return fuel
lines. Cover fuel lines using shop towel during removal as some fuel
may be retained. Remove vacuum hose from pressure regulator.
Disconnect injector harness from injectors.
3) Remove fuel delivery pipe, fuel injectors and pressure
regulator. See Fig. 3. DO NOT allow injectors to fall from delivery
pipe during removal. Remove vacuum hose and pipe assembly.
4) On Montero & Pickup, disconnect coolant temperature
sending unit, coolant temperature switch (A/C equipped), coolant
temperature sensor and thermoswitch (A/T equipped). Disconnect upper
radiator and coolant by-pass hoses. Disconnect heater pipe. On all
models, remove intake manifold and gasket.
Fig. 3: Exploded View of Lower Intake Manifold & Components
Courtesy of Mitsubishi Motor Sales of America, Inc.
Inspection & Installation
1) Inspect for damage and cracks on all mounting surfaces. To

\003
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.

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).

article, see appropriate HEATER SYSTEM article in the AIR
CONDITIONING & HEAT Section.
A/C SWITCH
Removal & Installation (Colt Vista)
From back side of control panel, push right control panel
clip right while pushing control panel out of dash panel. Allow
control panel to hang. Remove side bracket. Press temperature switch
control assembly left, and then remove A/C switch. To install, reverse
removal procedure.
Removal & Installation (Montero)
Remove lap heater duct. Remove glove box stoppers and glove
box. Remove heater control knobs. Remove center panel screw hole
plugs, and remove screws. Remove center panel. Disconnect center panel
wiring harness. Remove A/C switch. To install, reverse removal
procedure.
Removal & Installation (Pickup & Ram-50)
Remove heater control knobs. Remove glove box. Remove center
panel mounting screws. Use a trim stick to remove upper side of panel.
Remove A/C switch assembly mounting screws. Pull switch assembly
toward vehicle interior. Remove switch. To install, reverse removal
procedure.
COMPRESSOR
Removal & Installation (Colt Vista)
Discharge A/C system using approved refrigerant
recovery/recycling equipment. Disconnect high tension cable from
ignition coil. Remove distributor cap. Loosen idler pulley adjusting
bolt, and remove belt. Disconnect compressor electrical connector.
Remove high and low pressure lines and "O" rings from compressor.
Remove compressor mounting bolts. Remove compressor. To install,
reverse removal procedure.
Removal & Installation (Montero, Pickup & Ram-50)
DischargeA/C system using approved refrigerant
recovery/recycling equipment. Loosen idler pulley, and remove belt.
Disconnect compressor electrical connector. Disconnect high and low
pressure lines from compressor. Remove compressor mounting bolts.
Remove compressor. To install, reverse removal procedure.
CONDENSER
Removal & Installation (Colt Vista)
Discharge A/C system using approved refrigerant
recovery/recycling equipment. Remove front grille and grille brackets.
Remove front end cover and condenser harness. Disconnect electrical
fan connector. Slowly disconnect pressure lines from condenser. Remove
2 condenser mounting bolts. Lift up and remove condenser from vehicle.
To install, reverse removal procedure.
Removal & Installation (Montero)
Discharge A/C system using approved refrigerant
recovery/recycling equipment. Remove radiator grille. Slowly
disconnect pressure lines from condenser. Disconnect condenser fan
motor connector. Remove condenser fan mounting bolts and motor. Remove
condenser mounting bolts. Remove condenser from vehicle. To install,
reverse removal procedure.
Removal & Installation (Pickup & Ram-50)

Fig. 14: Manual A/C-Heater Wiring Diagram (Colt Vista)