Trouble Diagnosis Procedure For A/C System

TROUBLE DIAGNOSIS PROCEDURE FOR A/C SYSTEM

Inspection Flow:

SYMPTOM:
- A/C system does not come on.

MAIN POWER SUPPLY AND GROUND CIRCUIT CHECK

Component Description





Automatic Amplifier (Auto Amp.)
The auto amplifier has a built-in microcomputer which processes information sent from various sensors needed for air conditioner operation. The air mix door motor, mode door motor, intake door motor, blower motor and compressor are then controlled.

The auto amplifier is unitized with control mechanisms. Signals from various switches and Potentio Temperature Control (PTC) are directly entered into auto amplifier.

Self-diagnostic functions are also built into auto amplifier to provide quick check of malfunctions in the auto air conditioner system.





Potentio Temperature Control (PTC)
The PTC is built into the A/C auto amp. It can be set at an interval of 0.5° C (1.0° F) in the 18° C (65° F) to 32° C (85° F) temperature range by pushing the temperature button. The set temperature is digitally displayed.

DIAGNOSTIC PROCEDURE

SYMPTOM:
- A/C system does not come on.








Auto Amp. Check
Check power supply circuit for auto amp. with ignition switch ON. Measure voltage across terminal Nos. 26, 27, 33 and body ground.








Check body ground circuit for auto amp. with ignition switch OFF. Check for continuity between terminal Nos. 32, 14 and body ground.

If OK, check auto amp. ground circuit.
- If NG, check 7.5 A fuses (Nos. 11 and 24, located in the fuse block) and 15 A fuses (Nos. 1 and 2, located in the fuse block).
- If fuses are OK, check for open circuit in wiring harness. Repair or replace as necessary.
- If fuses are NG, replace fuse and check wiring harness for short circuit. Repair or replace as necessary.

NOTE:
If OK, replace auto amp.
If NG, repair or replace harness.