If you're low on the R134 coolant, your compressor clutch will not engage. If your sort of low it will turn on/off causing the surging you mentioned. Get a can of R134 from walmart with the recharge hose & guage and try charging your AC system. The low pressure side valve is like right in front of the battery on the AC line running across the front of the engine bay. Turn on the AC and start filling it, you'll probably see the clutch engage after a few minutes. (It takes a while...)
