I have a york heat pump model #E1RA030S06D that will not go in the defrost mode.it is fully charged.I pulled the cover off and noticed the red thero.wire was not connected to the other red wire.I don't know if it come unconnected or not,it looked as though it was connected with a wire nut at one time.will it hurt to reconnect to the larger red wire to see what happens?thanks for any help

I'm a little afraid to answer yes to this question. Installers (in my experience)use what ever wires are available. The red thermostat wire should be 24V from the dual fuel kit or air handler and should go to the 24V terminal of the PC board in the heat pump. The H.P. PC board does need a constant 24V to go into defrost.