As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOPILOT WOULD NOT CAPTURE NAV OR SLOW TO CAPTURE. AUTOPILOT WOULD DRIFT FROM PROPER COURSE WHEN CAPTURED. THIS WAS DUE TO INCORRECT HSI MODE RELAY INTERFACE WIRING FOR GPS. WIRING WAS INTERRUPTED AT AUTOPILOT FLIGHT DIRECTOR FD 112V AND SHOULD HAVE BEEN INTERRUPTED AT THE BACK OF THE NR 1 NAV RECEIVER. THIS AUTOPILOT IS A COLLINS AP106.