Trying to start up a water to air heat pump. The high side r-22 kicks out at 400psi within 3 seconds whether in cooling mode or heating mode. The reversing valve (alco 401RD-10F57) clicks but seems to be the only obstruction that would prevent refrig. Flow. There seems to be no suction side change. This unit has been sitting new/unused/charged for 10 years prior to installing (as a replacement to an identical unit)
Thank you for any suggestions or insights.
Tkornylak

Check to see if it has a liquid side pump down selonoid valve on it. If it does it has to be energised for the refrigerant to flow. Could also be a dead TXV power head.

Thank you. There are no pumpdown selonoids. What are the possible tests for the TVX and is it repairable?

Disconnect sensor bulb and hold in hand to heat up. The refrigerant should flow. If not then the TXV is defective.

Have you checked the suction and discharge valves to make sure they are open?(sounds funny but I have seen that before on a replacement)
Could the unit be overcharged?