My ac unit runs when thermostat is set to heat - I dont have a heat pump?

My ac unit works properly when the thermostat is set to cool - but when my thermostat is set to heat, and I turn it to heat in the winter, my furnace kicks in (correctly), shortly afterward my furnace fan kicks in (correctly) as does the fan in my ac unit outside (wtf?). I do not have a heat pump and activity should be controlled by the thermostat vice turning off the breaker (as low voltage still kicks in and the ac unit buzzes all winter when the furnace fan is engaged). please help. I've been told itd wiring/backfeeding and also told its a relay for 300 bux. any way to test this prior to spending the money?