A/C Request "A" Circuit Low

Possible causes

• CommonWiring or connector fault between the climate module and the engine module
• CommonFailed A/C request switch or climate control panel
• CommonCorroded connector
• CommonLow refrigerant, so the climate module never requests the compressor
• PossibleFault in the climate control module
• RareFailed engine module input

What you might notice

• Air conditioning not working
• Compressor never engaging
• Compressor engaging when not requested
• Idle speed not rising with the compressor, so the engine dips
• Check engine light on

What to check, in order

1. Disconnect at one end and check whether the low reading persists at the harness.
2. Check whether the climate control panel is actually asking for cooling - watch the request state on the live data screen while switching the air conditioning on.
3. Have the refrigerant charge checked. A climate module that knows the charge is low will not request the compressor at all, and that looks like a circuit fault.
4. Inspect the connectors at both modules.
5. Check the wiring between the climate and engine modules.
6. Note that the engine module raises idle speed when it accepts an A/C request. If the idle does not lift when the compressor engages, that confirms the request is not arriving.