These mechanical accelerometers wear over time and can cause unexpected autopilot disconnects.
On the P210N (and I’m guessing other Cessna 210 models) it’s located under the copilot’s seat. A round access panel with 6 screws comes off the floor, and the g-switch is located inboard of that panel. 4 screws through the floor hold the g-switch in position.
There’s a D-Sub connector on the g-switch. Pins 1 and 9 are part of the interlock loop that must be closed all the way through to keep the autopilot connected. If the g-switch is suspected of breaking the loop, you can temporarily jumper pins 1 and 9 to test the autopilot without the g-switch removed from the interlock.
Randy @ Auto Pilots Central in Tulsa, OK is an expert on this autopilot, and can repair the g-switches.