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Trim tabs not working-gctid400851

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    Trim tabs not working-gctid400851

    I am running an '88 2556 I was on the water today and my tabs quit working and I know nothing about them. I think the port one quit a few weeks ago but I hardly ever use that one but the one I need stopped working g today and now my back is killing me due to a 50 mile trip leaning to starboard. Can someone give me some ideas on how to diagnose the problem. I don't even know what type they are but I am sure they are original. Any help would be great.

    Oh yeah I do have power to the switches and neither set of switches work. I did at least check that.

    I think you have Bennett Trim Tabs on your boat.

    Take a look at the pump for the Trim Tabs, this picture will let you identify what brand you have;

    The first thing thing to check is to make sure both ends of the black ground wire at the pump are clean and tight.

    Here is a basic diagram of the system;

    Here is a link to a video that covers how the system works and troubleshooting

    This video covers "No Noise From The Pump"

    Below you will find troubleshooting you can print and take to the boat. Step 3 is a good place to start. And since it is an older system also do step 6.

    Let me know what you find and I will be delighted to help you get them functioning properly.

    Tom McGow

    Bennett Marine

    Fluid: Automatic Transmission Fluid (ATF) any type. Hydraulic Power Unit is self bleeding, running the Trim Tabs up and down 3-4 times will purge air from the system.

    Fuse: 12 volt system use 20 amp in-line fuse on positive. (24v & 32v use proportionately smaller)

    Red= Port Valve

    Green= Starboard Valve

    Blue=Motor Forward (pump pressure)

    Yellow= Motor Reverse (pump retract)

    Black on HPU=Ground

    Orange on Helm=Control Positive


    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:


    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.

    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.(Note: the interrupter relay is no longer used in current Bennett Trim Tab systems and has been replaced with a Switches that "lock out" preventing a blown fuse).

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      Thanks a lot for that information I now have working tabs again. You were right I do have Bennet tabs and that will be nice to know for future reference. You have been a big help and I really appreciate you taking the time. This a great Site and i am really happy to have the help. Thanks again