york model ef4h does not go into defrost

by Jimmy
(chesapeake va )

I have a york model e4fh heat pump in the house i just purchased durning the summer the ac stopped company came and looked at it and said a wire had came loose on the control board.The wire in question looked like it had never been hooked up but anyways ac started working with no issues. Now that winter has arrived the unit heats ok but it ices up on the outside coil and never goes into defrost i have done some research on the defrost board and it has been updated from a yorkguard IV to a yorkguard V. How do i make sure the wiring is correct before i purchase a replacement board and find out i still have the same issue? all of the wiring diagrams i can find on the gen v module show more wires than i have...My unit is running 4 wires into the 10 terminal block they are white going to the w position orange going to the w1 position red going to the w2 and brown going to the b/c position