How to Wire a Bennett Trim Tab Rocker Switch
The Bennett trim tab rocker switch is a straightforward two-pole, two-position momentary switch commonly used on boats with electric trim tabs. The basic principle is simple: flipping the switch one way raises one tab and lowers the other, and flipping it the other way does the reverse. But getting it wired correctly the first time matters, because a mistake here can leave your tabs stuck in a half-trimmed position or cause the pump to burn out. I've wired maybe thirty of these over the years across various boats, and the most common issue I see isn't the switch itself. It's the wire gauge and the lack of a proper relay setup. The rocker switch handles low current for the indicator lights, but if you're trying to run the tab pump through it directly, you're going to have a bad time. The contacts inside these switches are rated around 10 to 15 amps, which sounds fine until you account for the inrush current of a 12-volt tab pump motor. That startup spike alone can weld the contacts shut over time.
Understanding the Bennett Trim Tab Rocker Switch Wiring Diagram
The wiring diagram for most Bennett rocker switches follows a standard configuration. You'll typically see four or five terminals depending on whether the switch has built-in pilot lights. Let me walk through the four-terminal version since that's the most common one people are working with. Terminal 1 and Terminal 2 are your power feeds. Terminal 1 connects to the positive side of your battery through a fuse, usually 15 to 20 amps depending on your pump's amperage draw. Terminal 2 goes to ground or negative, but only if your switch has those built-in position indicator lights. Those lights need a ground path to illuminate when the switch is in either position. Terminal 3 and Terminal 4 are your output leads to the tab solenoid valve. When you press the switch forward, Terminal 1 closes to Terminal 3, sending power to one side of the solenoid. At the same time, Terminal 2 (if you have indicator lights) closes to Terminal 4, completing the circuit for the other side. Reverse the switch and the polarity flips. The solenoid valve shifts, the pump pushes fluid in the opposite direction, and your tabs move accordingly.
Here's something most diagrams don't make clear: the internal contact arrangement in these switches is not symmetrical in the way you might expect. The switch doesn't simply reverse polarity at the solenoid. It actually swaps which side of the solenoid gets hot while the other side stays grounded through the pump motor. This matters because if you wire it assuming a full positive-negative reversal at the solenoid, you'll get strange behavior where the tabs only move in one direction or not at all. The solenoid valve is a two-position spool, and it one hot leg to shift. The return spring handles the rest. One practical detail that saved me a weekend project on a 28-foot bay boat: I discovered the manufacturer's diagram labels the terminals A, B, C, D rather than 1, 2, 3, 4. I had the switch upside down on my workbench and spent twenty minutes tracing wires that went nowhere before I realized the terminal layout was mirrored from how I'd laid it out. Always verify terminal orientation against the actual switch body, not just the printed diagram. Another thing the diagrams gloss over is the importance of using inline fuses within six inches of the power source. I've seen multiple installations where the fuse was tucked behind the console, two feet away from the battery positive terminal. If a wire chafes and shorts before the fuse, you're not protecting anything. A six-inch rule keeps the exposed conductors minimal and makes fault isolation much easier later.
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Step-by-Step Wiring Process
Start by identifying what you're working with. Bennett makes a few variations of these switches, and the terminal layout can differ slightly between the standard rocker and the version with integrated LED indicators. Check the part number on the switch housing before you buy any wire or connectors. The part number is usually molded into the plastic bezel on the back side. Next, run your power feed from the battery through an appropriately sized fuse holder. For a typical tab pump drawing 8 to 12 amps under load, 10-gauge wire is standard. If your pump is larger, like on a boat with big hydrofoil tabs, bump up to 8-gauge. Don't skimp here. Voltage drop over long runs will make your tabs respond slowly, and you'll blame the switch when the real issue is undersized wire. Route the fused positive lead to Terminal A (or whatever your specific diagram calls it). Route a separate ground wire from the switch mounting location to a clean, paint-free metal point on the hull or frame. These switches need a solid ground reference for the indicator lights to work properly. A corroded ground point will make the lights dim or flicker, and you'll spend hours troubleshooting the switch instead of just scraping paint off a bolt hole.
Connect your solenoid valve wires next. Most Bennett tab systems use a two-wire solenoid. One wire goes to Terminal C and the other to Terminal D. The solenoid body itself grounds through its mounting bracket to the pump housing, so you don't need a separate ground wire for it. Make sure that bracket contact is clean metal-to-metal. I learned this the hard way on a friend's boat where the solenoid was mounted over a painted surface with a lock washer that hadn't been broken through. The tabs worked half the time and refused to move the other half. Scraped the paint, added a star washer, problem solved. After everything is connected, test before you mount the switch permanently. Use a multimeter to check continuity between the terminals in each switch position. In one position, you should see a direct connection from the power input to one solenoid output. In the other position, that connection should shift to the other solenoid output. If both positions show continuity to the same terminal, something is crossed. Double-check every connection before you button things up. One limitation worth noting upfront: these rocker switches are not waterproof. The IP rating is typically IPX4 at best, which means splash resistant, not submersible. If your switch is mounted in an area where waves wash over the console or where high-pressure washing is routine, plan to install a weatherproof cover or relocate the switch to a drier position. I've replaced three of these switches in five years, and two of those failures were from water intrusion into the terminal cavity. The third died from contact erosion after about eight years of normal use, which is closer to expected lifespan.
If you need a wiring diagram for reference, Bennett publishes theirs on their website under the support section for each product page. The diagrams are basic line drawings and they don't include wire gauge recommendations or fuse sizing, so you'll need to supplement them with your own research based on your pump's specifications. The diagram will show you the terminal connections, but it won't tell you why your tabs are moving in reverse order or what to do when the solenoid clicks but the pump doesn't run. For those answers, you need experience, not a PDF. The whole process, from unboxing to final test, usually takes about 45 minutes to an hour for someone who's done it before. First timer should budget two hours and keep a multimeter handy. If you're replacing an existing switch and the old wiring is intact, it can go faster, but I'd still recommend verifying the existing wire gauge and fuse rating before reconnecting anything. Previous owners cut corners, and finding out your existing 18-gauge wire is the weak link after you've already mounted the new switch is not a good feeling.
