Morning. My Ruud heat pump is set at 72 degrees.. outside temp is 4 above. The fan will not shut off. Do I need to switch my control to emergency heat or just let it run?

If the outside heat pump unit is running and it is 4 degrees above zero the heat pump should have shut down completely. It would be best to call for ON Site service so they can replace/add a outside thermostst control to the heat pump to turn it off when it is out of its operating range. This feature might already be installed or controlled by another means but it is malfunctioning and something the average home owner will not be able to track down and repair.

Is your EM heat at least coming on? Generally, when the EM heat comes on the HP should shut down, so in the meantime I would switch to EM heat until you can have it looked at. At 4F your HP is just running up your electric bill.

4 degrees? Does it really get that cold in Hawaii?