Circuit Description
The PCM cycles the A/C compressor clutch in order to optimize the performance of the A/C system. The PCM determines when to cycle the A/C compressor clutch by monitoring the A/C Refrigerant Pressure sensor.
The A/C Refrigerant Pressure sensor is also used by the PCM in order to enable the cooling fans when the A/C compressor head pressure reaches a predetermine value.
The PCM energizes the A/C compressor clutch when the engine speed is less than 4300 RPM and the A/C system is requested. If you request the A/C at engine speeds greater than 4300 RPM, the PCM will not energize the A/C compressor clutch until the engine speed decreases to less than 3950 RPM.
Any one of the following conditions disables the A/C compressor clutch.
| • | The throttle is commanded to Wide Open Throttle (WOT). |
| • | The A/C head pressure is greater than 2854 kPa (414 psi). |
| • | The A/C head pressure is less than 241 kPa (35 psi). |
| • | The ignition voltage is less than 10 volts. |
| • | The engine speed is greater than 5594 RPM. |
| • | The engine coolant temperature is greater than 125°C (257°F). |
The PCM also disables the A/C compressor when curtain DTCs set.
Diagnostic Aids
Inspect the harness going to the A/C clutch and going to the PCM for intermittent connections. While the engine is operating with the A/C enabled, move related electrical connectors and harnesses. This may aid in locating an intermittent fault.
For an intermittent, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests if the PCM can turn the A/C compressor ON.
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This step tests for an A/C refrigerant pressure sensor that is at a fixed value (stuck).
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Test the connections at the compressor first if the scan tool indicates that the A/C clutch is ON.
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Inspect the A/C clutch status circuit before replacing the A/C refrigerant pressure sensor. Also, a low refrigerant charge in the A/C system can cause a A/C system performance condition.
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The PCM's A/C clutch status circuit may not detect voltage when the A/C is commanded ON if the B+ supply circuit to the A/C relay is intermittent. Inspect the relay connections and operation.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
|
Important: If DTCs P0530, P1545, and P1546 are set, use those tables.
Does the A/C clutch engage? | -- | |||
Did the A/C High Side pressure increase more than the specified value when the A/C controls were turned ON? | 4 psi | Go to Diagnostic Aids | ||
Did you find and correct the condition? | -- | System OK | ||
|
Important: Before replacing the sensor, test the A/C system for the correct charge. An A/C system that does not have the correct charge will cause DTC P0530 to set. Replace the A/C Refrigerant Pressure Sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in HVAC Systems Manual. Is the action complete? | -- | System OK | -- | |
6 | Does the scan tool indicate the A/C clutch ON? | -- | ||
Repair the intermittent A/C clutch circuit from the A/C relay to the splice. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | System OK | -- | |
8 |
Does the test lamp illuminate? | -- | ||
9 | Probe the A/C compressor clutch B+ supply circuit to the A/C compressor clutch ground circuit using the test lamp J 35616-200 . Does the test lamp illuminate? | -- | ||
10 | Repair the faulty A/C clutch connection or the open A/C clutch coil. . Refer to Repairing Connector Terminals in Wiring Systems. Is the action complete? | -- | System OK | -- |
11 | Repair the open or the shorted A/C clutch B+ supply circuit. . Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | System OK | -- |
12 | Repair the open A/C clutch ground circuit. . Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | System OK | -- |
