Heater System: Other Isuzu Trooper II

Fan Control Knob

Knob controls fan speeds to regulate amount of airflow. Fan can be operated at 4 different speeds.

Airflow Selector Knob

Depending on position selected, airflow can be directed to different areas of passenger compartment. Airflow selection capabilities include individual areas or a combination of windshield, upper body, knee and/or foot area.

Air Source Selector Lever

Lever controls intake of outside air or recirculation of inside air.

Temperature Control Knob

Knob controls blend-air door position. Depending on knob position, airflow is directed through heater core (hot setting), around heater core (cold setting) or through and around heater core, resulting in modulated temperatures between full hot and full cold. (Scheme 4)

Scheme 4

MODE CONTROL CABLE

Turn select knob to defrost setting. Connect damper cable with mode control link of heater unit at defrost position. Secure cable using clip. Check airflow selector knob operation. (Scheme 5)

Scheme 5

TEMPERATURE CONTROL CABLE

Turn select knob to maximum cold setting. Connect cable with temperature control link of heater unit at cold setting. Secure cable using clip. Check temperature control knob operation. (Scheme 6)

Scheme 6

AIR SOURCE CONTROL CABLE

Slide select lever to left. Connect control cable to blower assembly control link at the recirculation position. Secure cable using clip. Check air source selector lever operation. (Scheme 7)

Scheme 7

NO HEAT OR INSUFFICIENT HEAT

Blower motor inoperative. Engine coolant temperature low. Insufficient engine coolant. Insufficient engine coolant circulation. Clogged heater core. Airflow does not pass through heater core. Improper or disconnected duct connections.

CONTROL LEVER MOVES BUT MODE DOOR IS INOPERATIVE

Cable clip not properly installed. Defective control link on heater unit or blower assembly.

MODE DOOR POSITION INCORRECT

Defective control link on heater unit or blower assembly. Control cable not adjusted properly.

BLOWER MOTOR INOPERATIVE

1. Check blower motor fuse in dash fuse/relay block. Check blower motor relay, blower motor resistor and blower switch. See BLOWER MOTOR RELAY, BLOWER MOTOR RESISTOR and BLOWER SWITCH under TESTING. If blower motor fuse, relay, resistor and switch are okay, check blower motor. See «BLOWER MOTOR»(ref-37713-S29455537842001010900000) under TESTING.
2. If blower motor is okay, start engine. Turn on blower fan. Check voltage at Blue wire terminal of blower motor harness connector. If battery voltage is not present, repair open Blue wire between blower motor fuse and blower motor harness connector.
3. If battery voltage exists, check for poor ground or open circuit in Blue/Black wire between blower motor and blower resistor harness connectors. Also check Black wire between blower switch harness connector and body ground.

BLOWER MOTOR INOPERATIVE IN CERTAIN POSITIONS

1. Check blower motor resistor. See «BLOWER MOTOR RESISTOR»(ref-37713-S39848777952001010900000) under TESTING. If resistor is not okay, replace resistor. If resistor is okay, check blower switch. See «BLOWER SWITCH»(ref-37713-S09798227792001010900000) under TESTING. If blower switch is okay, go to next step. If blower switch is not okay, replace heater control panel.
2. If blower does not operate in low speed, check for open Blue/White wire between blower motor resistor and blower switch harness connectors. If blower motor does not operate in medium-low speed, check for open Blue/Yellow wire between blower motor resistor and blower switch harness connectors.
3. If blower does not operate in medium-high speed, check for open Blue/Orange wire between blower motor resistor and blower switch harness connectors. If blower motor does not operate in high speed, check for open Blue/Red wire between blower motor resistor and blower switch harness connectors.

BLOWER MOTOR DOES NOT SHUT OFF

1. Check blower switch. See «BLOWER SWITCH»(ref-37713-S09798227792001010900000) under TESTING. If blower switch is not okay, replace heater control panel. If blower switch is okay, check following wiring harness for short circuits.
2. Check Blue/Black wire between blower motor resistor and blower motor harness connectors. Check Blue/Red wire between blower motor resistor and blower switch harness connectors. Check Blue/Orange wire between blower motor resistor and blower switch harness connectors.
3. Check Blue/Yellow wire between blower motor resistor and blower switch harness connectors. Check Blue/White wire between blower motor resistor and blower switch harness connectors.

BLOWER MOTOR RESISTOR

Disconnect resistor. Check resistance between indicated terminals. See BLOWER MOTOR RESISTOR TEST table. (Scheme 8) If resistance is not as specified, replace resistor.

BLOWER MOTOR RESISTOR TEST

Scheme 8

BLOWER SWITCH

Disconnect blower switch connector. Check continuity between indicated switch terminals. See BLOWER SWITCH TEST table. (Scheme 9)

BLOWER SWITCH TEST

Scheme 9

BLOWER MOTOR

Disconnect 2-pin connector from blower motor. Connect positive battery terminal to Blue wire terminal. Connect negative battery terminal to Blue/Black wire terminal. Ensure blower motor rotates. Replace motor if it does not rotate.

BLOWER MOTOR RELAY

1. Disconnect blower motor relay from dash fuse/relay block. With an ohmmeter, check for resistance of 85-105 ohms between relay terminals No. 1 and 3. (Scheme 10)
2. Check continuity between terminals No. 2 and 4. Continuity should not exist. Apply battery voltage between terminals No. 1 and 3. Ensure continuity exists between terminals No. 2 and 4 with voltage applied. Replace relay if continuity is not as specified.

Scheme 10