There are a few other items that control the AC besides the pressure sensor and PCM. Depending on the system either manual or automatic AC control. The manual uses a pressure sensor, temperature sensor the BCM, ECM and the IPDM to control the AC. The manual system is simpler in that it controls the compressor by using the intake temperature sensor in the HVAC box to tell it when it is hot or cold outside. Then you select cold and the BCM sends a signal to the IPDM and that activates the relay which in turn activates the compressor. The pressure sensor just tells the ECM if the system pressure is high or low. If you have the automatic AC (set a temperature and it does the rest) you have more sensors to control the system. As your compressor works the next thing would be to use a scan tool that has bi-directional control ability and use it to activate the pieces of the system to narrow down where the problem is. So you would select it to turn on the compressor, if the compressor turns on then the BCM, IPDM and control network is OK. Then you would look at the interior temp sensor, the intake temp sensor and the sunload sensor to see if one or more is the problem. The scan tool would also show if there were any error codes related to the HVAC system. Without it testing is limited to swapping some expensive parts. The images are the wiring for both the manual and automatic systems. The others are the sensors for either version. The IPDM is the underhood power module, the AC relay and compressor relays are soldered to the circuit board inside. It also needs a scan tool to be replaced.
Images (Click to enlarge)
Aug 24, 2026 at 6:32 PM
