ac 800m controller program washes away every time it restarts.
There is screw on the top right front of the Controller open this and then slide the top cover then you will find there is small battery inside which is normally with these spec
Built-in back-up battery
Type: Lithium, 3.6 V, 0.95 Ah, size 1/2 AA (it's easyily avilable in the local markets)
just take this one out and insert new battery and close the cover. when your battery will be healthy then "B" lite with stop blinking and it will be stable like run and other lights. Your controllr suppose to be on UPS power (highly recommeneded)