Our a/c quit blowing cold air, and was blowing hot air, figureing it was the thermostat malfunctioning we shut power off to the furnace and the ac began cooling again, we replaced the thermostat 2 days later, and now need the heater, and can't seem to get it to blow hot air now, furnace is heating, compresser still kicks on, could this be an issue in the compresser, rather than the thermostat?

I feel you have your low voltage wiring improperly hooked up. That needs to be fixed before you start looking at the units for problems.