Upon arrival, system isnlocked out on high pressure code. Reset system and hook up guages. Upon initial fireoff, the system immediately goes into high pressure lockout without turning on. Further investigation shows that high pressure switch has failed and is not making internal contact. High pressure switch needs replaced. Install new high pressure switch to take over for current faulty high pressure switch. Test run operation of system and verify no high pressure is actually happening. Refrigerant discharge pressure did not show any signs of higher than normal pressure. System is operating in heating mode at this time.