Diagnosis; Heating Cycle Diagnosis; Fan Control Lever (Fan Switch) Diagnosis - Isuzu Trooper 1999 Workshop Manual

1A–8 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Diagnosis

Heating Cycle diagnosis

Condition
No heating or insufficient heating.
Control lever moves but mode door
does not operate. does not operate
The mode door cannot be set to the
mode selected.

Fan Control Lever (Fan Switch) Diagnosis

Current flows to the blower motor through the heater and
the A/C relay (B-36) to activate the rotation of the blower
motor by turning "ON" the fan control knob (fan switch).
Blower motor speed is controlled in stages by the resistor,
by operating the switch from "LOW" to "HIGH".
Possible cause
Blower motor does not run or runs
improperly.
Engine coolant temperature is low.
Insufficient engine coolant.
Circulation volume of engine coolant
is insufficient.
Heater core clogged or collapsed.
The heater cores is not provided with
air sent from the blower motor.
Duct connections defective
unsealing.
Cable attaching clip is not correct.
Link unit of heater or blower
assembly defective.
Link unit of heater unit or blower
assembly defective.
Control cable is not adjusted.
For the inspection of the relays, switches and units in
each table, refer to "INDIVIDUAL INSPECTION" in this
section.
Correction
Refer to "FAN CONTROL LEVER
(FAN SWITCH) DIAGNOSIS".
Check the engine
temperature after warming up the
engine and check the thermostat.
Replace as necessary.
Add engine coolant as required.
Check if the water hose to the heater
core is clogged, collapsed or twisted.
Repair or replace as necessary.
Clean or replace as necessary.
Repair the temperature control link
unit or mode doors.
or Repair or replace as necessary.
Repair
Repair
Repair.
Adjust.
coolant