A/C Does Not Come On

TROUBLE DIAGNOSIS PROCEDURE FOR A/C SYSTEM

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




INSPECTION FLOW

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 mode door motor, air mix 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.

MAIN POWER SUPPLY AND GROUND CIRCUIT CHECK
Power Supply Circuit Check
Check power supply circuit for air conditioner system.




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, see below.
If NG, repair or replace harness. Check 7.5A fuse (No.5), 10A fuse (No.8) (located in the fuse block) and 15A 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.