how to test a.c. control unit

do u have a signal coming out of the module to turn on the relay for ac ? get a wiring diagram and look for power and ground supply to unit but i dont think that is the problem....... there is a low pressure cut off switch i think by the accumulator but they may have changed it around but look at a diagram look for the wires should be on the lines some where and find out the power and signal wire to the computer and jumper those terminals and then turn on the ac like u normally would if it goes on it is because the system pressure is low and control unit wont turn it on to save compressor from destroying itself if it does u have to get dye injected to the system and r-134a and run the system and use a black light to find the leak then repair and charge system and enjoy

I have the same problem with my 99. take off the control unit itself and look at the leads on the circuit thing. the temp one on mine fried off so that could be the problem