Upright Freezer. Freezer belongs to a friend in another city. I looked at it a few weeks ago and

Question

Freezer belongs to a friend in another city. I looked at it a few weeks ago and replaced the 9 volt battery that keeps the memory ( I guess that is it's purpose ). The battery only lasts a week and the red trouble light on the door comes on. No error codes appear on the key pad and the freezer maintains setpoint. What could be draining the battery? Thanks.