1991 MITSUBISHI MONTERO heater

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.

Disconnect harness connector from resistor terminals. Using
an ohmmeter, check resistance between terminals indicated in BLOWER
MOTOR RESISTOR RESISTANCE table. See Fig. 8. If resistance is not as
shown, replace resistor.
BLOWER MOTOR RESISTOR RESISTANCE TABLE









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Terminal Nos. Ohms
Montero
1-2 ..................................... 1.22
1-3 ...................................... .41
1-4 ..................................... 2.25
1-5 ........................................ 0
Pickup & Ram-50
1-2 ..................................... 1.19
1-3 ...................................... .50
1-4 ..................................... 2.33
1-5 ........................................ 0









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Fig. 8: Identifying Blower Resistor Terminals
Courtesy of Mitsubishi Motor Sales of America.
REMOVAL & INSTALLATION
HEATER CORE

Removal (Montero)
1) Move temperature control lever to WARM position. Drain
coolant from vehicle. Disconnect heater hoses from heater unit. See
Fig. 1.
2) Remove lap heater ducts. Remove hood release bracket.
Using screwdriver, release tabs and remove left and right demister
grilles. Remove glove box frame attaching screws, and remove glove
box. Remove passenger lap heater duct.
3) Using screwdriver and shop towel, carefully pry at top
center of instrument cluster cover, and remove cover. Remove 2 screws
at bottom of instrument panel and one bolt at top of instrument panel.
Gently pull instrument cluster out, and disconnect speedometer cable
and electrical connections. Remove instrument cluster.
4) Remove 4 screws, and disconnect electrical connections on
back of instrument cluster. Remove instrument cluster. Handle
instrument cluster carefully. Instrument cluster can be damaged if
dropped.
5) Remove center console knobs and side screw plugs. Remove
screws, disconnect electrical connections and remove console. Remove 6
bolts and console bracket (center dash reinforcement). Disconnect
radio connections while removing console bracket.
6) Remove horn pad and steering wheel retaining nut. Mark
steering wheel and steering shaft for reassembly reference. Using
steering wheel puller, remove steering wheel.
7) Using screwdriver, carefully pry out dash plug at upper
center of dash panel. Remove 3 upper dash mounting nuts, one upper
screw above steering column, and 2 lower mounting screws. Remove dash
panel.
8) Remove control cables at heater unit. Remove heater unit
attaching screws. Remove heater ducts. Remove heater unit. Remove
heater control lever arm.
9) Remove heater control valve cover. Remove heater pipe and
heater control valve. Disconnect control arm linkage. Remove control
arm. Remove heater core by moving it sideways.
Installation
1) To install, reverse removal procedure. Insert heater hoses
fully into pipes, and clamp securely to prevent leaks. Connect heater
hoses with 1-1.2" (25-30 mm) overlap on outlet.
2) When filling radiator with coolant, first open heater
control valve fully and run engine to circulate coolant and discharge
air from inside heater and engine cooling system. Stop engine, and add
coolant.
3) Adjust all control cables. When installing heater hose
grommets, apply sealer. After installing heater control assembly,
ensure each lever operates smoothly.
Removal (Pickup & Ram-50)
1) Disconnect battery ground cable. Place heater control
lever to far right. Drain coolant. Using trim stick, pry out hazard
switch and remove electrical connection. Remove 4 instrument cluster
cover screws, and remove cover. Remove 4 instrument cluster screws.
Tilt instrument cluster out, and disconnect speedometer cable and
electrical connections. Remove cluster.
2) Remove fuse box cover and fuse box assembly. Remove glove
box. Remove defroster air ducts. Disconnect heater control cables.
Using trim stick, pry under and remove speaker grilles. Remove clock
or coin box in center of dash. Remove center dash hole cover (located
above clock).
3) Remove 2 center support cover screws, and remove cover.
Remove shift knob and 6 console attaching screws. Remove console.
Ensure all electrical connections are free of dash panel. Remove 3 top
nuts, one bolt above steering column, and side and lower attaching

screws. Remove dash panel.
4) Remove blower duct, center duct and defroster ducts. See
Fig. 2. Disconnect heater wiring harness from heater unit. Remove
heater center support brackets. Remove heater unit. Remove heater core
cover plate and joint hose. Remove heater core from heater unit.
Installation
1) To install, reverse removal procedure. Insert heater hoses
fully into pipes, and clamp securely to prevent leaks.
2) When filling radiator with coolant, first open heater
control valve fully and run engine to circulate coolant and discharge
air from inside heater and engine cooling system. Stop engine, and add
coolant.
3) Adjust all control cables. When installing heater hose
grommets, apply sealer. After installing heater control assembly,
ensure each lever operates smoothly.
HEATER CONTROL PANEL
Removal (Montero)
1) Remove heater control knob and heater fan switch knob.
Remove center console. Remove defroster nozzle at temperature control
cable side.
2) Remove lap heater duct and glove box stopper, and push
glove box forward and down. Disconnect inside/outside control cable
from blower assembly.
3) Disconnect control cables from heater unit. Remove heater
control panel mounting screws, and pull out panel slightly. Disconnect
heater fan switch harness connectors. Remove heater control panel.
Remove heater fan switch from heater control panel.
Installation
1) Place air outlet change-over lever at closed position.
With heater side air outlet change-over damper lever in position,
connect inner cable to lever, and secure cable casing using clips.
2) Place heater control lever at OFF position. With heater
control lever in position, connect inner cable to lever, and secure
cable casing using clips.
3) Place inside/outside air change-over lever at INSIDE
position. With heater side inside/outside air change-over damper lever
in position, connect inner cable to lever, and secure cable casing
using clips.
4) Set control lever to each position to check for correct
operation. If lever does not operate correctly, adjust by moving outer
wire at clipped point. Ensure each control lever moves smoothly. If
any noise or stiff movement exists, apply multipurpose grease to all
moving parts.
NOTE: When mounting heater control panel to instrument panel,
tighten upper bolts to instrument panel so they also secure
center panel.
Removal & Installation (Pickup & Ram-50)
Remove cluster panel. Remove all control cables at heater.
Remove heater control panel. To install, reverse removal procedure.
Adjust cables as necessary.
WIRING DIAGRAMS