The average car today contains a bewildering range of sensors that feed information to various computers to monitor everything from air intake to emissions and engine timing. Your car’s air conditioning system also contains a couple of sensors that manage operation. However, unlike oxygen sensors, MAP sensors and others on your car, they don’t feed information to the computer. You can’t “pull a code” on an air conditioner malfunction.

Air conditioning components

There are two primary components that manage the operation of your car’s air conditioning system. The first and most important is the AC compressor. This component is responsible for pressurizing the system during operation. It also adjusts based on your input – when you change the temperature in the cabin through the HVAC control panel. The clutch operates the compressor based on your settings (but it doesn’t really “sense” whether the system is working or not).

The second component is the clutch cycling switch. This is a safety switch designed to keep the system off if there is not enough refrigerant for safe operation. It’s also designed to monitor the temperature inside your car’s evaporator core to ensure that they don’t drop low enough to freeze the entire core (which would stop AC operation).

Both of these components play a role in temperature monitoring and control, but neither of them communicates this information to the car’s computer. Diagnosing an automotive air conditioner problem will require a professional diagnosis of the symptoms (blowing hot air, not blowing at all, noise from the compressor, etc.), and then a complete inspection of the entire system coupled with a check of refrigerant levels, often with a special UV dye to detect leaks.

This article originally appeared on YourMechanic.com as What Sensors in the AC Tell the Car If the System Is Working or Not? and was authored by Valerie Johnston.


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