1991 MITSUBISHI MONTERO Service Manual

REFILLING
To prevent air from being trapped in engine block, engine
should be running when refilling cooling system. After system is full,
continue running engine until thermostat is open, then recheck fill
level. Do not overfill system.
TESTING
THERMOSTAT
1) Visually inspect thermostat for corrosion and proper
sealing of valve and seat. If okay, suspend thermostat and thermometer
in a 50/50 mixture of coolant and water. See Fig. 1. Do not allow
thermostat or thermometer to touch bottom of container. Heat water
until thermostat just begins to open.
2) Read temperature on thermometer. This is the initial
opening temperature and should be within specification. Continue
heating water until thermostat is fully open and note temperature.
This is the fully opened temperature. If either reading is not to
specification, replace thermostat.
Fig. 1: Testing Thermostat in Anti-Freeze/Water Solution
PRESSURE TESTING
A pressure tester is used to check both radiator cap and

complete cooling system. Test components as follows, following tool
manufacturer's instructions.
Radiator Cap
Visually inspect radiator cap, then dip cap into water and
connect to tester. Pump tester to bring pressure to upper limit of cap
specification. If cap fails to hold pressure, replace cap.
Fig. 2: Testing Radiator Pressure Cap
Cooling System
1) With engine off, wipe radiator filler neck seat clean.
Fill radiator to correct level. Attach tester to radiator and pump
until pressure is at upper level of radiator rating.
2) If pressure drops, inspect for external leaks. If no leaks
are apparent, detach tester and run engine until normal operating
temperature is reached. Reattach tester and observe. If pressure
builds up immediately, a possible leak exists from a faulty head
gasket or crack in head or block.
NOTE: Pressure may build up quickly. Release any excess pressure
or cooling system damage may result.
3) If there is no immediate pressure build up, pump tester to
within system pressure range (on radiator cap). Vibration of gauge
pointer indicates compression or combustion leak into cooling system.
Isolate leak by shorting each spark plug wire to cylinder block. Gauge
pointer should stop or decrease vibration when leaking cylinder is
shorted.

HEA TE R S YSTE M

1991 M it s u bis h i M onte ro
1991-92 HEATER SYSTEMS
Chrysler Motors, Mitsubishi
Chrysler Motors: Ram-50
Mitsubishi: Montero, Pickup
DESCRIPTION
Heater assembly on all models is located in passenger
compartment. A heater control valve is used to regulate coolant flow
and heat output. Heater assembly contains heater core, heater control
valve, air ducts, blower motor and intake ducts. See Fig. 1 or 2.
Heater systems are blend-air type.
Fig. 1: Identifying Heater System Components (Montero)
Courtesy of Mitsubishi Motor Sales of America.

Fig. 2: Identifying Heater System Components (Pickup & Ram-50)
Courtesy of Mitsubishi Motor Sales of America.
OPERATION
Heater and fresh air operations are controlled by knobs on
some models and control levers on others. The control panel of models
equipped with control levers consists of mode control levers for
inside/outside air, temperature control, air selector and multi-speed
blower switch.
The temperature control opens and closes heater control
valve, which determines heat output. Heater mode control directs
heated air to windshield when in DEF position, to floor when in HEAT
position, or to center ventilation ducts when in VENT position. Bi-
level output is possible by positioning lever between VENT and HEAT
positions.
TEMPERATURE CONTROL LEVER
Temperature level is selected by sliding lever left or right.
Highest heat setting is when selector lever is in WARM position. With
temperature lever set at COOL position, ambient air is used for
ventilating.
AIR SELECTOR LEVER
This lever is used to select source of air flow into vehicle.

With lever set at OUTSIDE position, outside air is allowed to enter
and/or pass through heater. With lever set at INSIDE position, air is
recirculated inside passenger compartment.
BLOWER SWITCH
The blower can be operated at different fan speeds to
regulate amount of air forced through vehicle. Fan speed will increase
as switch is turned or moved right.
AIR CONTROL INDICATION SYSTEM
This system consists of indication lights built into
instrument cluster and 4 switches connected to various control levers.
An indication light glows when heater blower is on. Lights also
indicate choice of outlets and whether air source is inside or outside
vehicle. In addition, temperature of air directed from outlets is
indicated for each air outlet by light colors of green (cool air) and
orange (warm air).
ADJUSTMENTS
HEATER (TEMPERATURE) CONTROL VALVE
Place control lever to indicated position. See TEMPERATURE
CONTROL CABLE ADJUSTMENT table. See Fig. 3. Connect cable to heater
control valve and/or air damper lever according to table. Secure cable
sleeve using clips. With engine running, check for coolant leaks and
check operation of heater control valve. If heater control valve does
not operate properly, adjust by moving cable sleeve forward or
backward at retaining clip.
TEMPERATURE CONTROL CABLE ADJUSTMENT TABLE









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Application Control Lever Water Valve
Position Lever Position
Montero .................... Far Left ............... Toward cable
Pickup & Ram-50 ............ Far Left ........ (2) Away from cable
(2) - Disconnect link between air damper lever and water valve
lever. Close water valve. Close air damper. Reconnect link.
Attach cable to clip.









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Fig. 3: Adjusting Temperature Control Cable (Typical)
Courtesy of Mitsubishi Motor Sales of America.
INSIDE/OUTSIDE AIR SELECTION CABLE

Move control lever to INSIDE position. Connect cable to
damper lever with outside air intake to heater closed. Apply
multipurpose grease to rotating portions of sliding lever. Check for
proper damper operation by moving control lever. To adjust, press air
control lever toward cable and move outer wire at retaining clip. See
Fig. 4.
Fig. 4: Adjusting Air Selection Cable (Typical)
Courtesy of Mitsubishi Motor Sales of America.
MODE SELECTOR LEVER
Place selection lever in DEF position, and remove cable clip.
Ensure defroster door is fully open. Secure cable sleeve using clips.
Move lever to other positions to check for correct operation. Adjust
cable, if necessary, by moving sleeve forward or backward at retaining
clip.
TROUBLE SHOOTING
BLOWER MOTOR INOPERATIVE
Blown blower fuse. Blower motor improperly grounded.
Defective switch or faulty blower motor wiring connections. Foreign
object in fan.
INSUFFICIENT HEAT

Incorrect thermostat in cooling system. Improperly adjusted
temperature control cable. Clogged heater core fins. Faulty heater
control valve.
NO TEMPERATURE REGULATION
Clogged or stuck heater control valve. Incorrect installation
of heater control valve control cable. Incorrect adjustment of heater
control valve link.
NO VENTILATION
Incorrect adjustment of change-over dampers. Duct connection
loose.
TESTING
BLOWER MOTOR SWITCH TEST
Blower motor switch can be tested using an ohmmeter. Insert
test leads into appropriate connector terminals, and check continuity.
See BLOWER SWITCH CONTINUITY table. See Fig. 5 or 6.
BLOWER MOTOR SWITCH CONTINUITY TABLE









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Continuity Between
Switch Position Terminal Nos.
Montero
Low ................................ 1-2 & 1-7
Medium 1 ........................... 2-4 & 4-7
Medium 2 ........................... 2-5 & 5-7
High ............................... 2-6 & 6-7
1992 Montero
Low ................................ 1-8 & 3-5
Medium 1 ........................... 1-8 & 5-6
Medium 2 ...................... 1-4, 1-8 & 2-5
High .......................... 1-4, 1-8 & 5-7
Pickup & Ram-50
Low ........................... 1-2, 2-6 & 7-8
Medium 1 ...................... 1-3, 3-6 & 7-8
Medium 2 ...................... 1-4, 4-6 & 7-8
High .......................... 1-5, 5-6 & 7-8









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Fig. 5: Blower Motor Switch Connector Terminal ID (Pickup & Ram-50)
Courtesy of Mitsubishi Motor Sales of America.

Fig. 6: Blower Motor Switch Connector Terminal ID (Montero)
Courtesy of Mitsubishi Motor Sales of America.
BLOWER MOTOR TEST
1) Turn ignition on. Check fuses. If fuses are bad, check
wiring harness for short circuits. If fuses are okay, check voltage
between heater relay and ground circuit. If voltage does not exist at
heater relay, check for broken wire between fuse block and heater
relay.
2) If voltage exists at heater relay, check relay, and
replace if necessary. See BLOWER MOTOR RELAY TEST under TESTING. If
relay is okay, disconnect blower motor connector. Set heater switch to
either LO, MED or HI setting.
3) Check voltage between harness side of connector and
vehicle ground. Battery voltage should be present. If battery voltage
is present, go to next step. If battery voltage is not present, check
continuity between resistor terminals. See BLOWER MOTOR RESISTOR TEST
under TESTING. If continuity is not present, replace resistor.