Hi I have a central air and heater unit and when I turn it on for heat or air at the thermostat nothing happens. Can you help me?

Check if the thermostat had the wiring connected, this might be caused by meltdown of the wires as the time ages. Or the thermostat might be broken. Though I am not certain what might be the problem as there are many things that can go wrong. Such as there is a short circuit, or the heater is broken. Check the manual of the central air conditioner and look up the manufacturer. You may call them and ask them for specific assistance but that will cost money.

Hi thanks for the info, I already change the thermostat, so I guess it could be a short circuit in the wire or the heater. I check the heater manual and contact them
Thanks