Thermostat wiring for an older packaged Heat Pump....help please?

[cdwinaz]

I have and older ICP sngle stage packaged rooftop heat pump with no aux. heating. There are 4 wires coming from the unit.
The wires at the unit are :
G - Fan
R - 24V power
O - Reversing valve
Y - Condenser

At the new Honeywell digital hermostat (for hearpumps)
I connect the R to the R/Rc terminals (has a jumper)
I connect O to the O terminal
I connect the G to the G terminal
Now the problem:
When I connect the Y to the Y terminal I get cooling but not heating (compressor doesn't engage in heat cycle). OR when I connect the Y to the W terminal I get heating but not cooling.

Any ideas what I'm doing wrong?

Thanks in advance for any help.