'03 with manual A/C. All control settings work ok, but air output on A/C settings is not cold. There is no P0530 code, which I would expect if the pressure in the system was low. Under the hood, the compressor clutch won't engage, relay just keeps clicking. Any wisdom on this, before I give up and take it to the shop?

 

Your '03 will not set a P0530, it is not equipped with a pressure monitoring sensor.


What is the low side pressure with the system off? If it's below ~42psi, the clutch will not engage.


Is the cycling switch on the accumulator clicking when the AC is on?


With the engine at idle, Mode switch set to MAX AC, unplug the compressor clutch connector. One wire should show battery voltage, the other should show less than 5 ohms resistance to ground.

 

From my 2003 FSM:

DTC P0530

Circuit Description

"The Powertrain Control Module (PCM) monitors the high side refrigerant pressure via an A/C refrigerant pressure sensor. When the pressure is high the signal voltage is high. When the pressure is low, the voltage is low. When the pressure is high the PCM commands the cooling fans on. When the pressure is too high or too low the PCM will not allow the A/C compressor clutch to engage."

You may want to be sure of your info before refuting my statement.

 

I'm very familiar with the function of the sensor and circuit. There are certain GM vehicles that have it. However, on S/T body (1983 through 2005) the circuit is not shown in the schematic, and the data stream shows N/A, (not applicable) on a scanner. Good luck finding it on yours though.