Mercury – Auxiliary Dash Switch Harness (Duals) | Trim Switch Interface | 84-866704T01

Overview
This harness gives dual-engine DTS boats a clean way to add an auxiliary trim switch at the dash. It plugs in between the 8-pin trim connector and the command module harness, so there’s no splicing or guesswork. The setup is straightforward—just plug it in and your extra trim control is ready to use. It’s a simple add-on that keeps the wiring tidy and makes trim control easier to reach.

Key Features
    • Auxiliary Trim Switch Harness – Provides the wiring path for an added dash trim switch.
    • Dual-Engine DTS Use – Built for two-engine Digital Throttle and Shift systems.
    • In-Line Mounting – Installs between the 8-pin trim connector and the command module harness.
    • No Diode Trim All – Direct trim-signal connection without “trim-all” logic.
    • OEM Connectors – Factory plugs that lock in and stay secure.

Engine & Boat Compatibility
    • Digital Throttle and Shift
    • Dual engine
    • Auxiliary dash-mounted trim switches

Performance & Practical Benefits
Having a second trim switch on the dash makes day-to-day running a bit easier, especially when you want quick access without reaching for the throttle handle. The harness keeps the wiring organized and avoids the messy look of improvised connections. Trim response stays steady since the signal follows a clean, direct path.

Why Buy OEM
OEM harnesses plug in exactly the way Mercury designed, so you avoid loose fits, odd trim behavior, or wiring headaches later. They hold up well to vibration, heat, and spray, giving you long-term reliability.

FAQ
Q1: How do I know I need this harness?
A: If you’re adding an auxiliary dash-mounted trim switch to a dual-engine DTS setup, this is the harness that ties it in.

Q2: Does it require calibration?
A: No—just plug it in and the trim system works normally.

Q3: Saltwater safe?
A: Yes. Rinse occasionally and keep the connectors clean.

Q4: Any installation tips?
A: Mount it where the harness won’t rub on sharp edges, and leave a little slack for movement.

Q5: What are early signs of harness issues?
A: Slow trim response, intermittent operation, or visible wear on the cable jacket.