Dale
Glad to hear you are taking it to a shop! There are a number of excellent shops that are still very familiar with the 400B. It was used in all the 400 series aircraft incl. the 414.
Make an accurate list of the problems and insure they understand.
Secondly it is worth a test flight with them to check the roll limits, capture and GS lock capability. IT is capable of fully coupled approaches. If you have the flight director then have them set up the command bars. You should be able to intercept the loc at 45 degrees and fly a full approach to the MAP (hands off), hit the go-around button and see the command bars jump to 15 deg , uncouple, pitch up and fly the outbound. If not ... then don't leave until it does.
Test fly and make sure it does a max rate one either left or right before you get there. This way they can eliminate messing around with the AI /GYRO.
Make sure they take out the gyros and do a clean and relubricate all 3 servos.
One last point. Have them replace the small blue connector on the flux gate compass which has been prone to corrossion due to dissimilar metals. The new ones today have gold plated pins that will not corrode. At least have them check it. it is outboard on the port wing. It is a bit tricky to get at. It can cause havoc and cost time and money to find.
Half the problem is pilots go in and say "it doesn't work". That fine ... if you want to spend lots of money and waste technicians time.
Never send out a computer for repair without insuring it for the cost of a new autopilot. Losing it can be a disaster!
http://www.avionicswest.com/articles..._autopilot.htm
is worth reading.
Bob