M20C ARC Autopilot trouble

[Taracka]

I have a 63 M20C with the ARC single axis autopilot. The problem I am having is as follows. When I switch the autopilot on there is a rapid clicking sound coming from the actuator mounted under the panel that sounds like the electromagnetic clutch not wanting to engage. If I turn the heading knob on the autopilot to the heading that doesn't require the autopilot to command a heading change the clicking slows to a stop and the actuator will then engage and start fuctioning normally. I removed the actuator and disassembled the case halves finding nothing I would consider abnormal. I'm thinking either the electromagnetic clutch is failing or the voltage that supplies it may be inadequate indicating whatever drives it could need adjustment. Does anyone on this forum have experience with these units and if so could give me advice on what else I might check?

Thanks,

Rich

[KSMooniac]

Wish I could help, but I didn't even know any ARC autopilots made it into Mooneys! Brittain was the only one as far as I knew for vintage Mooneys. Good luck!

[N201MKTurbo]

With a century servo, the electro magnetic clutch pulls a gear aganst another gear. If the mechanism is jammed or the gear teeth are really warn it will jump teeth whrn it tries to run. This kind of sounds like what you describe.

[63-C-]

Arc 512 autopilot is very similar to an early cessna nova-matic 300...wiring diagrams and connectors are the same. Rapid clicking sounds like an intermittent electrical connection or a failing clutch to me...measure voltage at the connector on the servo under the left instrument panel when you switch the knob to omni or heading mode....cannot remember which pin it is but its only like an 8 pin connector...there should be a constant power & ground, a + right, +left, motor feedback 2 wires, & a clutch solenoid enguage that will be + 12v when the unit is turned on. Use a digital volt meter so you do not damage anything. I did just remove a complete Arc 512 system from my 63c that I would be willing to sell as whole or parts if you are in need. I can let you know pin #s when i am back at work if you like. Good luck