What is an “AC Reset” and How to DIY

What is an AC reset on a quartz watch?

An AC (aka All Clear) reset, system reset, or circuit reset is a function to reset or clear the settings or other information that may be stored in the watch’s integrated circuit (aka IC) after a battery change.

Why do I need to do an AC reset?

Seiko describes a system reset like this:

“When a battery is replaced with a new one, or when the battery is removed and reinstalled following the repairing procedures, the information stored in the IC of the circuit block will be disordered. As a result, digital quartz may show an abnormal display, and the hands of analogue quartz may not move properly. To return the watch to normal, it is necessary to reset the circuit following a certain procedure depending on calibers. Such procedure is generally referred to as ‘system reset’ or ‘all clear (AC)'”. -Source: Seiko Service Bulletin, No. 16, April 1991; Quartz Watch System Reset: Necessary Procedure After Battery Change

How to do an AC circuit reset on my watch?

Not all quartz movements have a AC reset or system reset feature.

You may see the letters AC engraved next to a hole in the plate of the movement. This is for short-circuiting the movement after a battery change, to clear any information still embedded in the system.

Other watches may have a system reset procedure that involves a specific sequence of moving the crown or pressing the buttons.

The method of performing a system reset depends on the caliber. Many of the caliber listings on this site give instructions on how to do an AC reset.

Videos:

Casio G-Shock AC Reset Tutorial:

Another good example of a G-Shock AC reset procedure: