A step-by-step diagnosis for a car with a faulty AC: customer information, weighing the refrigerant, fault codes, vent temperature and line pressures.
MSG Equipment shares a diagnostic algorithm for when a car arrives with an allegedly faulty air conditioner. The first step is to get as much information as possible from the owner about when symptoms began and when the system was last serviced.
- Check whether there is refrigerant in the system and determine the amount by weighing it, not by pressure.
- Review AC-related fault codes and sensor readings in the control unit.
- Run the system at steady maximum load; the centre vent should read about 5–10 °C depending on ambient temperature.
- Measure low- and high-side pressures in different modes; at 20–25 °C ambient expect roughly 2–4 bar and 10–15 bar.