One of our site residents posted the following from Bennett:
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I am Thomas and I work for Bennett Marine in Client Services. I am sorry for the trouble you are having with your trim tab system, but from the description it sounds like an electrical connection fault that can be tested out very easily!

Since your Port tab is working we know the motor/pump assembly is ok. The system is setup with an electric motor that runs Forward (Blue wire) and Reverse (Yellow wire) to provide the down and up action for the trim tabs. It also has two solenoid valves to separate which tab to be moved. There is a Red wired one for Port and a Green wired one for Stbd, just like navigation! I believe you are not getting power on the Blue wire when operate your control to move your Stbd tab, since the only noise you hear is a click from the Stbd solenoid when it opens. Please take a monument and check the backside of your control and ensure all of your connections are good and without corrosion. Then check the rest of the wiring down to the Hydraulic Power Unit (HPU) for the same thing. From your description I believe you either have a Rocker Switch Control (two side-by-side rocker switches) or the Racing Type Control (4 round rubber buttons in a square bezel housing). If so, within 1' of the HPU you MAY found a small gray box with gray potting which would be our Interrupter Relay. If you find one, please bypass it and try testing the system with your controls. If no change, then conduct the following tests with it bypassed. The following is a Trouble Shooting Guide for the system:

Red = Port Valve
Green = Stbd Valve
Yellow = Motor reverse, tab(s) up
Blue = Motor forward, tab(s) down
Orange = Power, located at trim tab control
Black = Ground, found on backside of HPU

Please conduct the following hot wiring tests starting at the trim tab control and working your back the HPU. Ensure you are working with proper voltage (12 volts for most systems, 20 amp fuse):

Blue + Red + Power = Port tab down
Blue + Green + Power = Stbd tab down
Blue + Red + Green + Power = Both tabs down
Yellow + Red + Power = Port tab up
Yellow + Green + Power = Stbd tab up
Yellow + Red + Green + Power = Both tabs up

Please get back to me with your findings and with the age of your system, since it has a 5 year warranty! You can contact me at the email address or phone number below.

I look forward to your reply.

Sincerely,
MJ Thomas
Bennett Marine, Inc.
Client Services
954-427-1400
954-480-2897 Fax[edited]