Autopilot problems and upgrades?

[Petehdgs]

I own a 1964 Super21 that has an OEM Nav-O-Matic 300 autopilot.  It has been working but I noticed it did not work in cold temperatures.  When I started having the same problems with my AI and DG I concluded the grease or oil in the instruments was getting old, so I pulled both instruments and the AP Gyro and sent them out for repair.  After repairs My Autopilot does not stabalize the aircraft and tends to roll.  This is possibly a bad pickup inside the Gyro.  I intend to send it back to Mid-continent Avionics and ask them to re-examine it, but because of the age it may not be possible to get parts or expertise to resolve it.   

Has anyone here had and OEM Nav-O-Matic replaced with a more modern unit?   Were you happy with the results?  What kind of $$ was involved? 

I am basically looking for options here.  I don't use the AP all that much, but if possible I would still like it to be available if possible.  

 

Thank you all in advance.  

[N201MKTurbo]

I believe the pickup coil in that gyro is different than most gyros. They may have put a standard coil in. They both have the same plugs.

[Raymond J1]

At each intervention on the reference instruments (TC for brittain or similar, AI, DG for king or similar) it is sometimes necessary to review the gain and offset settings of the autopilot controller, in particular for deviations of less than 5 ° of heading, where the turn setpoint is at reduced rate (1/2) and not at normal rate (1). Failing that, the plane does what you describe, that is to say too important heading excursions.

Edited December 17, 2022 by Raymond J1