300/500 series alarm?

My alarm system has developed a fault I thought it was the battery (dated 2011)which I have now renewed but the fault remains. The master keypad is showing a steady 86 instead of Un(when unarmed )and the smaller keypad is flashing rapidly between 86 and Un. It is setting and unsetting quite normally,I just wish I could get the alarm to show steady lights ( UN ) when unset. My user manual states on the front GARDTEC 360/580