Nest Thermostat not working properly, check power to thermostat (base) getting 24 volts jumper r,y,g,and o heat pump started, check operation only running at 10 degree delta, check refrigerant pressures r22, unit is low on refrigerant, unit is from 1995 would recommend system replacement, home comfort consultant is set up for tomorrow 2 to 4 pm for new heat pump