I have a Cetrek 930 AP on a 43C. Don't know age, but the OPs Manul has a 1998 date. Unit has worked flawlessly for the 5 years I have owned boat. Over last month or so, it has become less effective at moving rudder and now no movement at all. Turns own, self tests successfully, compass works, engages pump and runs. But no rudder movement. I checked hydaulic steering fluid reservoir. There are 4 sight glasses on the reservoir in a vertical line. Fluid level is above bottom 2 and below top 2, as it has always been. PSI was 20, so I increased to 30. No change. My next thought is to remove and disassemble AP pump to check impeller. Before I do, any thoughts or suggestions?

I cannot find Cetrek on web. Anybody know if they still exist?