disconnected furnace, now AC doesn't work

Your problem is POWER (12 volt) to the Roof AC control board. Also, since you replaced the Wall tstat with a NON RV Tstat, that compounds your operation problem. Now, (Jayco RV's do this) they run the 12 volt positive to the FURNACE RED input wire. There are 2 BLUE wires coming out of the furnace for the Wall tstat. Those 2 Blue wires go to 2 smaller gauge wires going to the Roof AC control board OR to the wall tstat depending on how the OEM wired the system. Either way, it sends the 12 volts to the AC upper control board to operate it. Since you changed the Wall tstat, your 12 volt COMPRESSOR signal is NOT sent to the upper control board . But when you jump the 2 wires from the old furnace you send a 12 volt back feed signal to operate the fan---It takes 2 separate 12 volt signals to operate the FAN and the Compressor. And you should have Lo and Hi fan and you only have the signal for either at this time. The AC control board is what activated the furnace to run and cycle. The wall tstat sent a 12 volt signal to power that 2nd BLUE wire from the AC control board furnace relay. You will not burn out the AC unit by trial and error. You may blow the fuse for the AC control board, but will not damage the board. What you need to try at this point is to connect the furnace 12 volts to the OTHER blue wire and see if it functions. Disconnect the original blue wire you jumped. Doug