Bennett AC3000- Need Help

[JLR]

I bought this gizmo. It is a computer controlled device that raises and lowers my trim tabs based on sea conditions. I have had its predecessor units on my last five boats. It always worked well. But, not this one. It has three components, a control head, a keypad and a relay. Bennett has replaced all three components and each time, tested mine and said they could not find a problem. This last time, they tore down each component and said they were fine. So, I guess it must be my installation. Perhaps so. In a nutshell, I was unable to operate my tabs in the manual mode with their components installed. But, without their components, my tabs work perfectly. So, here are my questions.
First, the relay requires a constant 12v source. It also requires a 20 amp fuse in that source. I pulled the 12v from my high water alarm system. If that 12v source did not have enough amps either to power the relay or the pump, would it blow the 20 amp fuse? Mine never blew.
Second, since I am going to switch 12v sources, is there any reason not to jump the 12v source from the separate 12v source that ordinarily powers the pump from the pigtail before the relay?
Third, I also intend to move the control head away from its proximity to my autopilot pump. Could magnetic interference from my pilot pump mess up whatever is inside the control head that senses the boat attitude to activate the computer control of the tabs?
Sorry for the long post but I have been dicking around with this thing since February and each time I install it and take it out, it takes a few hours of my time. Thanks for the help.

 

[JLR]

Installed this for the third time hoping three times is a charm. I changed power sources to a 12v circuit with some oomph- taken from my salt water washdown. I also moved the control head away from my AP pump, hoping to avoid any magnetic field issues. And, I sanded down the contacts to the rocker switch hoping that helps. I will have my answer in a few days and will report back. If anyone has a like new Bennett rocker set for trim tabs with a square bezel and about six holes in it for mounting, I'd could use it as a replacement for the one I have now. Apparently, this "old style" set of rockers is no longer made and the new ones, while fitting in the hole for the old one, have a bezel that is a touch smaller.