I put a new thermostat in and the ac works right but the furnace won't fire up

I think that you would fair better as far as answers you receive if you were to post this question on the following link rather than on the Homework Help Other Subjects board.

https://www.askmehelpdesk.com/newthr...ewthread&f=150

Your question will get more noticed there.

>Moved to HVAC<

The proper response to a misplaced thread is to click on the report inappropriate post link at the upper right corner and ask to have it moved. A new thread only confuses things.

I suspect either you didn't connect the white wire to the thermostat, or you didn't connect the red wire to both RH and RC. For more details, see the sticky at the top of the Heating and Cooling forum.