York heat pump,Have cold air all summer,fan alone runs fine,emergency heat works great,But when you turn it to heat only it will blow fuse,could it be a control board on the inside... Thats what I'm being told now.. by a service tech... By the way THANKS for the help so far... Heater coils have been checked,could something be over looked at the heating coils? Has anyone ran across this problem before??

If it blows fuse for the whole unit, maybe heater element contacting gound.
If transformer fuse, check heat low voltage control wires or heat contactor shorted.