Good morning rmcnees,
Thank you for the followup information.
Couple things, the linear rudder reference unit in the past has had issues with corrosion. When an autopilot stops working that is using a linear rudder reference unit that is often times the source of trouble. There are a couple of things to do. First take good photos of the Linear RRU Installation on the engines, take good photos of the inside of the NavPilot Processor where all the wires are terminated and post them to this forum so we can look at what you are dealing with at all points. I have no doubt the the authorized dealer did a good job with the installation, I just want to verify what we are working with. Next we need to get an idea of what version of software the NavPilot 500 O/B is using. Please follow the steps below and report back what version of software. We also need to verify what Linear RRU is installed. It is probably a Teleflex RRU but we need to know the model number, please report back with that information.
There are some tests you can run on the RRU to measure the resistance it provides. If you have a multimeter available please follow the steps below to see what the reading are when the engine is in the hard over position.
Please remove the cover of the NavPilot Processor and then power the NavPilot on. The RRU terminal is labeled TB13. When the engine is center if you take a volt meter and put the probes across TB13-2 and TB13-4 you should see around 2.5 volts. Next turn the engine to hard over port you should see .5 volts. Turn the engine to hard over starboard and you should get around 5 volts. Please report back what readings you get.
2.) The heading sensor connection into the pilot processor. After further research it appears the NavPilot 500 came with (2) different cables for the PG500R compass. The cable you mention below has a fuse inline. I found an old service advisory, #04-04T where it recommends that the 2m cable that is fused not be used to power the PG500R directly from the processor. It recommends a different cable that does not have an inline fuse that is 10m. The part number for the 10m cable that should be used is: 000-159-681. Based on what you describe it sounds like there could be a short in the installed heading cable.
3.)When you ran the rudder test you got movement to the port then back to center but the test would not move the rudder to starboard. It is a reversing pump set, so if you motor is able to turn the vessel to port then it should be able to turn the vessel to starboard. This could indicate a couple of things. I believe the brushes in the motor are in a working condition because you get movement to starboard. There could be some sort of clog or plug on the starboard port in the pump manifold. You could always bypass the system test and directly put voltage to the reversing pump wires. This will move the rudder one direction, if you reverse the voltage it will move the pump in the other direction. This test would eliminate a clog in the manifold if you get rudder movement past center in both directions.
Do you know or can you see any signs of teflon tape used on the hydraulic connection points? Without knowing how your hydraulic system is put together we will not be able to guide you on advise with the hydraulic system. Typically if there is a reservoir that can be a point of fill up but the helm pump itself may require some fluid as well.
How does the vessel hand steer? Is it sloppy or pretty tight?