The A/C clutch relay is activated if the A/C switch is operated while the blower is running and system operation is enabled by the ECM. When A/C is requested, the Engine Control Module(ECM) provides a ground path to the A/C clutch relay control circuit. When the relay circuit is grounded, the A/C clutch relay is energized. The ECM delays grounding the relay circuit for a short time, so the ECM can adjust the engine idle speed for the additional load. The ECM will temporarily de-energized the A/C clutch relay for one or more of the following conditions:
- Full acceleration when the throttle is at WOT.(Wide Open Throttle)
- Risk of overheating: Engine coolant temp. exceeds threshold value.
- A/C system pressure exceeds threshold value.
- Engine starting.
ECM monitors inputted voltage through A/C compressor relay. Checking voltage every 10 sec. under detecting condition, if the voltage higher than the specified value is detected for more than 5 sec., ECM sets P0647.
Item | Detecting Condition | Possible cause |
DTC Strategy |
•
Detects circuit short to low voltage | 1. Poor connection 2. Open or short to ground in A/C relay circuit 3. Faulty A/C relay 4. Faulty ECM |
Enable Conditions |
•
After 0.5 sec under conditions below
•
No DTC exists
•
Engine works
•
11V ≤ Battery voltage ≤ 16V | |
Threshold value |
•
Short to power | |
Diagnosis Time |
•
Continuous (More than 5 seconds failure for every 10 seconds test) | |
MIL On Condition |
•
DTC only (NO MIL ON) |
Coil Resistance | 70Ω ~ 120Ω |
