I have a 2 ton split heat pump unit (unionaire brand) I have had many different repair people out and no one can seem to repair. The system will not cool or heat even though the compressor is coming on. The high side pressure is low and the low side pressure is high. One tech said it was a bad compressor and replaced it only to still have the same problem, $700.00 later he left scratching his head. I had another tech look at it and he told me it again has a bad compressor. I have a hard time believing this although just because it's new does not make it good? I just do not want to continue throwing parts and money at it. I have read a lot on the net on heat pump systems and found a couple threads that said the reversing valve could be stuck in such a position that the compressor would be circulating through itself. If I need to replace the reversing valve, is a valve a valve? If the line size and configuration and coil voltage is the same will it work?

Thanks for your help, Mark