Scan Climate Control Systems

Modern automatic climate control systems rely on sensors and actuators to achieve the driver’s desired results. Many scan tools are capable of displaying these input values in real time datastream. Datastream is great for spotting intermittent problems in A/C systems. They are also capable of bi-directional control. Bi-directional control allows the scan tool to communicate with the control module and actuate components like the compressor clutch, blend door, and blower motor.

Understand the values on the climate control mode of the scan tool.

The ECT sensor is displayed in volts. The value can be compared to manufacturer’s specifications. An engine coolant temperature sensor or ECT sensor is a variable resister that uses resistance to change a 5 volt reference signal from the PCM. The sensor's signal changes according to the engine's coolant temperature. It decreases as the engine warms to operating temperature.

Pressure sensors are transducers that convert refrigerant pressure to a variable voltage signal, somewhere between 0.1 V for low pressure (~0 psig) and 4.9 V for high pressure (~430 psig). Modern vehicles have sensors located on both sides of the system. Use a known good manifold and gauge set and a scan tool to diagnose sensor function. Armed with a scan tool a technician can monitor system refrigerant pressure without a manifold and gauge set.