We had an AC 800M controller fail. We had a spare and we are trying to set it up. We have powered it on the bench, and connected to it with the serial firmware upgrade. We can successfully load the firmware, but when we restart after the upgrade, the red led comes on and flashes as if there is a fault. The manual states this as a firmware upgrade in process or other issue. We can not use IP Config until we can get a firmware upgrade and restart. We do not have a battery in the unit, but I do not believe this should be an issue. The processor is an 866.

 

Probably it's broken, but if you can load firmware via serial cable you can connect a serial console like Putty the same way and see the messages it's printing while booting if you want details