My hvac unit does not seem to be working properly. The ac comes on when I turn it to ac and the blower/fan works when I switch from auto to on but when I switch it to heat nothing happens could this be a thermostat problem or could it be something in the unit is not receiving the signal from the thermostat to turn on or failing to turn on

You can remove the wires (2) from the tstat one that goes to w _post, the other goes to r -post tie them together, this bipasses the tstat, the furnace will come on and not turn off till you untie wires
. This tells you the furnace is OK. And the problem is in the tstat

Sorry, I should add, before removing wires,turn off power to furnace after tieing wire together turn power back on,