My old stat (Weathertron 3AAT80B1A1) has some bizarre (to me) connections.

F is connected to the White wire (? )
W is jumpered to X2 = black wire in
U is empty (has no wire coming in) but looks jumpered by mfr with a tiny soldered wire to the W and X2 bundle.
B=Blue
Y=Yellow
G=Green
O=Orange
R=Red
T= Tan (brown)

On my new White-Rodgers 1F97-1271 (says OK for single stage heat pump):

I can't figure out the black and white wires based on the old stat config.

Here' what I think I have:

Blue = C (24V common)
Orange = O (changeover valve energized cooling)
Yellow = Y (compressor relay)
? = W (heat relay (White? ))
Brown/tan - tape off
Red = RH/RH jumpered (power)
? = L (malfunction light) (ignore? )
? = B (changeover valve energized heating)
Green = G (fan relay)

Also suggests for heat pump use, I should jumper W and Y. then read somewhere online that I shouldn't. Should I?

Any help filling in the blanks would be much appreciated. Have never seen F ever used before, much less using the white wire...

Thanks again!

Here is the W/R install instructions.

http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-6664.pdf

Check the sticky notes at the beginning of this board with help on Thermostat wiring color and destination.

When F (usually fan) is white (usually 24V as hvac noted) something is confusing. Also sticky suggesting brown is common will hurt a lot of people. Brown is usually T a Trane exclusive, not common. Common is usually black or blue.