Neon L4-2.0L DOHC (1996)
A/C Signal: Description and Operation
Related Trouble Codes and Set Conditions
A/C Clutch Relay Circuit
Name of Code:
A/C Clutch Relay Circuit
When Monitored:
With the ignition key in the run position and battery voltage above 10 volts.
Set Condition:
An open or shorted condition is detected in the A/C clutch relay control circuit.
Theory of Operation:
The A/C compressor clutch relay controls the 12 volt source for the A/C clutch. The relay is located in the power distribution center. One side of
the relay control coil is supplied with 12 volts when the ignition switch is turned to the run position. The circuit is completed when the other side
of the relay coil is grounded by the powertrain control module (PCM). When A/C is requested, the PCM adjusts the idle speed to accommodate
the A/C compressor load on the engine. The PCM grounds the relay control circuit after the PCM receives an A/C request and adjustment of the
idle speed has been implemented.
Possible Causes:
-
Relay coil open or shorted
-
Fused ignition switch output circuit open
-
Compressor clutch relay control circuit open or shorted
-
Inoperative circuit driver in powertrain control module
A/C Pressure Sensor Volts Too High
Name of Code:
A/C Pressure Sensor Volts Too High
When Monitored:
With the ignition on, the engine running, and the A/C relay energized,
Set Condition:
The A/C pressure sensor signal at PCM cavity 42 goes above 4.9 volts.
Theory of Operation:
The A/C pressure sensor informs the PCM if the A/C system pressure is too low or too high. This information allows the PCM to determine if it
can engage the compressor clutch. If the A/C system pressure is too low, the PCM will not engage the compressor clutch. If the system pressure is
too high, the PCM will disengage the compressor clutch and turn on the cooling fans to prevent the compressor head pressure from becoming too
high. The sensor provides a signal to PCM cavity 42. The sensor receives a 5-volt supply from PCM cavity 61. The sensor ground is provided by
PCM cavity 43.
Possible Causes:
-
Sensor signal open
-
Sensor internally open
-
PCM failure
-
Open sensor ground
A/C Pressure Sensor Volts Too Low
NAME OF CODE:
A/C Pressure Sensor Volts Too Low
WHEN MONITORED:
With the ignition ON, the engine running, and the A/C relay energized.
SET CONDITION:
The A/C pressure sensor sensor signal at PCM cavity 42 goes below 0.7 volts.
THEORY OF OPERATION:
The A/C pressure sensor informs the PCM if the A/C system pressure is too low or too high. This information allows the PCM to determine if it
can engage the compressor clutch.
-
If the A/C system pressure is too low, the PCM will not engage the compressor clutch.
