Testing an Air Conditioner at Different Voltages Using A Variac

Testing the operation of an air conditioner at different voltages using a variac. The compressor didn't seem to respond much to the change in voltage. The speed remained generally the same, including it's ability to start, down to around 90 volts. A drop in speed started to take place around 70-80 volts, then it would stall. The fan motor showed much more response to the change in voltage, slowing considerably with even just a 10% voltage drop. There wasn't a significant drop in current; I suspect lowering the voltage would have an overall negative impact on the efficiency of the machine. And no, I don't believe this test did any damage to the machine. I think the only damage that could potentially occur would be if the compressor was slowed down enough to the point where the oil pump was no longer operating quickly enough to provide adequate lubrication. I'm not sure at what speed that would take place.