1991 MITSUBISHI MONTERO wiring

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

ENGINE COOLANT TEMPERATURE SWITCH
1) Turn engine off. Disconnect connector at engine coolant
temperature switch. Jumper wires on harness side of connector. If
vehicle uses a single connector, ground connector.
2) Press A/C switch to ON position and turn blower switch to
ON position. Momentarily turn ignition on and listen for compressor
clutch engagement. Clutch should engage. If clutch does not engage,
check fuse and other components wired in series with compressor
clutch.
EVAPORATOR THERMISTOR
Disconnect connector and remove thermo relay from evaporator
core. Jumper wires on harness side connector. Turn A/C switch to ON
position and turn on blower. Momentarily turn ignition on and listen
for compressor clutch engagement. If clutch does not engage, check
fuse and other components wired in series with compressor clutch.
HIGH PRESSURE SWITCH
Colt Vista
Disconnect high pressure switch connector. Jumper wires on
harness side of connector. Momentarily turn ignition on and listen for
compressor clutch engagement. If clutch does not engage, check fuse
and other components wired in series with compressor clutch.
HIGH/LOW PRESSURE CUT-OFF SWITCH
Pickup & Ram-50
1) Turn engine off. Disconnect High/Low Pressure Cut-Off
(HLPCO) switch, located on refrigerant line near condenser. Jumper
HLPCO wiring harness connector. Turn A/C switch and blower switch to
ON positions. Momentarily turn ignition on and listen for compressor
clutch engagement.
2) If compressor clutch does not engage, check evaporator
thermistor and engine coolant temperature switch. Check for a faulty
fuse. Repair or replace as necessary. If compressor clutch engages, go
to next step.
3) Connect manifold gauge set to system, and check operating
pressures. HLPCO switch should allow compressor operation if system
pressure is 28-385 psi (1.9-27 kg/cm
). If HLPCO switch does not
operate within specified pressure range, discharge system using
approved refrigerant recovery/recycling equipment, and replace switch.
4) After replacing switch, recharge system, and monitor
pressures for proper compressor function. If HLPCO switch cuts power
to compressor clutch while driving even though temperatures inside
have not yet decreased, high pressure side of new HLPCO switch has
possibly been activated. Go to next step.
5) Discharge system using approved refrigerant
recovery/recycling equipment. Replace switch, and recharge system.
Ensure compressor clutch operates within 28-385 psi (1.9-27 kg/cm
).
Check for sufficient system cooling.
LOW PRESSURE SWITCH
Colt Vista
Disconnect low pressure switch connector. Jumper wires on
harness side of connector. Momentarily turn ignition on and listen for
compressor clutch engagement. If clutch does not engage, check fuse
and other components wired in series with compressor clutch.

COMPRESSOR CLUTCH
Disconnect wiring to compressor clutch. Connect battery
voltage directly to A/C compressor clutch wiring harness connector
terminals. If a click is heard, clutch engagement is okay. If click is
not heard, pulley and armature are not making contact. Repair or
replace as necessary.
REAR BLOWER SWITCH
Montero
With blower switch in position indicated in REAR BLOWER
SWITCH CONTINUITY TEST table, ensure continuity exists between
terminals listed. See Fig. 8.
REAR BLOWER SWITCH CONTINUITY TEST TABLE









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Switch Terminal
Position Numbers Continuity
OFF ................. 1-6 ................. No
Low .............. 1, 2 & 6 .............. Yes
Medium 1 ......... 1, 3 & 6 .............. Yes
Medium 2 ......... 1, 4 & 6 .............. Yes
High ............. 1, 5 & 6 .............. Yes









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Fig. 8: Identifying Rear Blower Switch Terminals (Montero)
Courtesy of Mitsubishi Motor Sales of America.
REFRIGERANT TEMPERATURE SENSOR
Disconnect refrigerant temperature sensor electrical
connector. Using an ohmmeter, measure resistance between terminals. At

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. 13: Exploded View of Rear Evaporator Assembly (Montero)
Courtesy of Mitsubishi Motor Sales of America.
Removal & Installation (Pickup & Ram-50)
Discharge A/C system using approved refrigerant
recovery/recycling equipment. Disconnect liquid pipe and suction hose
connections. Remove glove box assembly. Remove air and defroster
ducts. Remove evaporator drain hose and clamp. Disconnect wiring
connectors. Remove nut from firewall evaporator assembly mounting
bracket. Remove evaporator assembly. To install, reverse removal
procedure.
WIRING DIAGRAMS

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

Fig. 15: Manual A/C-Heater Wiring Diagram (Montero)

Fig. 16: Manual A/C-Heater Wiring Diagram (Pickup & Ram-50)