I have been working on a good friend of mines 3 year old Armstrong heat pump the past couple of evenings and boy has it been a good one. The first day i showed up and found the compressor had shorted out causing a funky burnout, i go to the supply house the next day and pick up the warranty compressor and get it installed. Purged the lines, installed a new bi-flow liquid line drier, triple evacuated the system and dumped the factory recommended 410a charge into the system. Fired the compressor up and got equal pressures on the discharge and suction lines. Reversing valve was bad, come back the next day and put the dreaded reversing valve in the was also under warranty, triple evacuated, charged it back up. Fired the system up again everything is running good in cooling, adjusted the charge to 15* subcooling, 12* superheat, everything is looking good. Started packing my tools up in the truck and i told by buddy i wanted to check heat mode, compressor fired up and kicked out on high pressure within 10 seconds. I know i have a blockage in the system somewhere and i am pretty sure it is the condensing unit TXV, its the only thing that makes sense to me. I just wanted to run it by you guys to make sure i am not missing anything so i do not have to break the bad news to my buddy for the 4th time. Thanks in advance.