Unit will not power up. No BDi display. Hour meter is working and i check the wire harness that plugs in the back of the hour meter/ service panel and the fuse. Battery voltage is 24.I have checked both disconnect switches. The diode on the line contractor test ok. Line contactor ohms are 55. When i install the handset the code is COM (communication error). I have key on power to the controller. Anything else to check before I replace the controller? Fuses on the control panel test ok.