Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
A/C System, Operating After Charging
If the mechanically drivenAir Conditioning (A/C) compressor was removed, rotate it approximately 10 times by hand before using it for the first time (during or after installing, for example before installing the belt) to prevent damage caused by liquid impact when first switched on (any oil in compressor cylinder is forced out on rotation).
If the electronically driven A/C compressor was removed, activate it after filling the A/C compressor before the A/C system on via the "basic setting, compressor cut-in" function for the Guided Fault Finding. Refer to Vehicle Diagnostic Tester in the "Guided Fault Finding " Function for A/C System and Battery Regulation. This prevents the A/C compressor from being damaged, for example, by liquid impact when it is first switched on (any oil in the A/C compression chamber is forced out).
The vehicle engine drives the mechanically driven A/C compressor via a belt or shaft. The electronically driven A/C compressor is driven via an electric motor attached directly to the A/C compressor (for example on hybrid vehicles).
Operating an A/C System with a Mechanically Driven A/C Compressor
-- Start engine with compressor switched off (version with A/C clutch).
-- Set compressor to minimum output, for example, "Econ" or A/C off mode (version with no A/C clutch with regulating valve).
-- Wait until idle speed has stabilized.
-- Switch on the compressor and operate the system for at least two minutes at idling speed.
-- If necessary, check pressures in the refrigerant circuit using the A/C service station.
-- Turn the engine off.
-- Screw out the hand wheel on the quick-release coupling adapter.
-- Disconnect the charging hoses from the refrigerant circuit.
-- Install the caps.
Operating an A/C System with an Electrically Driven A/C Compressor
-- Operate the A/C compressor using "basic setting, compressor cut-in" in Guide Fault Finding. Refer to Vehicle Diagnostic Tester "Guided Fault Finding " A/C System and Battery Regulation.
-- After the basic setting and If necessary, check pressures in refrigerant circuit using A/C service station.
-- Screw out the hand wheel on the quick-release coupling adapter.
-- Disconnect the charging hoses from the refrigerant circuit.
-- Install the caps.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.