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Hi tabman im hoping you can help me. I have an 88 Grady White Trophy Pro with a bennett pump in it. I cant find the model # sorry. I went to try it out and the tabs worked at first but a few days later did not. One wont move at all and the other will not go up. We tried gently pushing on them but that didnt work either. The pump is full of ATF fluid, when I hit the switches I can hear the pump humming but get nothing at the tabs. The boat is out of the water, and was not used much by the previous owner, im almost done with its refit this is one of my last problems that needs to be worked out.
Thanks Kenny
__________________ "Your freedom to be you includes my freedom to be free from you." - Andrew Wilkow
I had the starboard Bennett tab stop working on me and read the manual and did a search on this forum for previous ideas (e.g. check for electrical, check for actuator problem, check for pump problem) and quickly was able to diagnose and repair. Look back at previous recommendations - seems to me electrical is a common problem when they fail. My problem wasn't because of Bennett equipment but the wiring I did pulled loose from behind the switch.
I pasted below what seems to be recommended means of diagnosing the problem:
Troubleshooting
1.If one side is not operating reverse hydraulic lines on the front of the Hydraulic Power Unit to determine if the malfunction is in HPU or actuator / hydraulic lines. If after reversing the lines symptom shifts to the other side the malfunction may exist in HPU. If the symptom remains on the same side, malfunction may exist with the actuator / hydraulic lines
2. Is the unit receiving a solid 12 volts? Low voltage will some times cause the solenoids to not open preventing the tabs from moving even though the pump motor is running.
3. Conduct the following test:
Remove the wires from the helm control and touch together as follows:
Operation=Reaction
Orange (+), blue, red= Port trim tab down
Orange (+), blue, green=Starboard trim tab down
Orange (+), blue, red, green= Both trim tabs down
Orange (+), yellow, red= Port trim tab up
Orange (+), yellow, green=Starboard trim tab up
Orange (+), yellow, red, green= Both trim tabs up
If the trim tabs function correctly for each wire grouping then the switch is at fault. Also note that any loose or missing screws on the back of the switch (whether a wire is connected there or not) can cause the pump to malfunction.
This test may also be done right at the pump by substituting a "hot lead" for orange. There is usually a connector to the wire harness within a foot or so of the pump. You want to check this connection for corrosion. You may wish to cut the connector off on the pump side and try the test on bare wires.
4. If you suspect corrosion on the wire connector near the pump, cut it out, test as above and reconnect using butt splices.
5. If you conclude the problem is in the pump, contact me. Bennett Trim Tab Systems carry a five year warranty. We also offer a trade in program for units out of warranty. Contact us for further details after you troubleshoot the system.
6. Check to see if there is a relay in line on the wiring harness near the hydraulic power unit. If there is it is an Interrupter Relay (IR1000). It prevents the system fuse from blowing if you try to actuate one trim tab up and the other down at the same time. After you test as outlined above, try removing the relay from the wiring harness and retest the unit. If it works the IR1000 will need to be replaced
HI tabman. I was finally able to check the tabs with those tips. The pump works we can hear it run and the lines going in and out of it flex when we hit the switch up and down. We also hear the pitch of the motor change with the switches. It seems like its something on the other end of the system when we try to move the tabs by hand one does and seems to have a spring in it, the other side does not move at all. The tabs worked about 6 months ago and the boat has been out of the water for a year now. Could the pistons on the stern have frozen up?? Thanks Kenny.
__________________ "Your freedom to be you includes my freedom to be free from you." - Andrew Wilkow
OK. The motor on the pump works, and one tab will now go up and down. We pulled the pump out and cleaned it and got it to pump atf in and out. Then we put it back in the boat both tabs worked, then we tried again and only one tab worked. Any tips for this one? It has us scratching out heads. Thanks
__________________ "Your freedom to be you includes my freedom to be free from you." - Andrew Wilkow
trouble shooting tips please! 
