Ce-560 flight crew reported the autopilot was climbing and descending on its own while at FL430.

Attributes
ACN	1389866
Time
Date	201609
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Citation V/Ultra/Encore (C560)
Operating Under FAR Part	Part 135
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Component
Aircraft Component	Autopilot
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude

Narrative:

After we leveled off at 43000 feet in cruise flight the autopilot pitched the nose up and aircraft climbed 160 feet and descended 160 feet. We descended to 40000 feet and it oscillated 80 feet. We descended to 38000 feet. It finally quit oscillating as bad. Maybe 40 feet here and there. We called maintenance and they had us take the plane to ZZZ instead of ZZZ1. We traded out airplanes and continued our flight to [our destination] with no other problems.

Original NASA ASRS Text

Title: CE-560 flight crew reported the autopilot was climbing and descending on its own while at FL430.

Narrative: After we leveled off at 43000 feet in cruise flight the autopilot pitched the nose up and aircraft climbed 160 feet and descended 160 feet. We descended to 40000 feet and it oscillated 80 feet. We descended to 38000 feet. It finally quit oscillating as bad. Maybe 40 feet here and there. We called maintenance and they had us take the plane to ZZZ instead of ZZZ1. We traded out airplanes and continued our flight to [our destination] with no other problems.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.