Rocker switches control accessory circuits in vehicles, boats, and equipment. A rocker switch pivots on a center axis, so one end sits down while the other sits up. Press the raised end, and the contacts inside change state. The action gives the switch its name and its flat, low-profile face.

The basic switching principle is simple, but the terminals become harder to identify because manufacturers combine built-in lamps and multiple switching poles in a single housing.

This guide covers four common configurations:

• A 3-pin lighted switch for 12V DC accessories

• A 5-pin switch with separate ON and dash lamps

• A 4-pin double-pole switch for 240V AC equipment

• A 7-terminal momentary switch for winch or solenoid control

Each section follows the exact example shown in the reference diagram.

Important: Pin count alone does not identify a rocker switch's terminal functions. Switches with the same number of pins may use different contact arrangements, lamp circuits, and terminal numbers. Confirm the part number and schematic printed on the switch, or map the switching contacts with a multimeter before connecting power. Carling's Contura range, for example, supports multiple single-pole, double-pole, maintained, momentary, and illumination arrangements within similar housings.

Read the Switch Before You Wire It

Terminal numbers are usually molded or stamped into the switch body. Do not assume that the number sequence matches a diagram found for another switch.

Before wiring:

1. Check the manufacturer's datasheet or the schematic printed on the switch.

2. Set a multimeter to continuity mode.

3. Probe the switching terminals with the rocker in each position.

4. Record which terminals connect in the ON, UP, and DOWN positions.

5. Identify lamp terminals from the manufacturer's schematic. LED lamps may be polarity-sensitive and may not behave like switch contacts during a continuity test.

6. Compare your recorded results against the wiring diagram before you connect power.

Tools and Materials

• Automotive or marine primary wire in the correct gauge

• Female spade terminals sized to the switch blades, commonly 0.250 or 0.187 inch

• Ratcheting crimp tool

• Wire strippers

• Multimeter

• Inline fuse holder and correctly sized fuse

• Adhesive-lined heat-shrink tubing for exposed connections

• Relay when the load exceeds the switch's applicable rating

Use flexible stranded wire in vehicles, boats, and other equipment exposed to vibration. Solid building wire is not intended for crimped vehicle harnesses.

Nassau National Cable stocks TWP, GXL, SXL, and TXL automotive primary wire, along with tinned marine wire for boat and saltwater installations.

How to Wire a 3-Pin Rocker Switch for 12V DC

Typical use: a single 12V accessory that needs on/off control with a status light, such as a cabin fan or a work light.

The switch shown in the diagram is an SPST on/off switch with a built-in indicator lamp. Two pins carry the accessory circuit, while the third provides the negative return for the lamp.

Example terminal functions

These labels apply only to the three-pin layout shown. Other three-pin switches may be SPDT switches without a separate lamp-ground pin.

Wiring steps

1. Disconnect the battery negative terminal or otherwise isolate the DC power source.

2. Run a positive wire from the battery or distribution point to an inline fuse.

3. Install the fuse as close to the power source as practical.

4. Connect the fuse output to the switch's POWER terminal.

5. Connect the ACC or LOAD terminal to the positive lead of the accessory.

6. Connect the accessory's negative lead to the vehicle's negative return or chassis ground.

7. Connect the switch's GND terminal to the same negative system.

8. Reconnect the battery and test the circuit.

In this example, the lamp receives positive power from the switched output, so it illuminates when the switch and accessory are on.

If the accessory works but the indicator remains dark, check the lamp-ground connection and confirm that the switch uses the same internal layout as shown in the diagram.

How to Wire a 5-Pin Lighted Rocker Switch

Typical use: a multi-switch panel that must remain readable in the dark. Off-road and marine dashboards use this configuration so the legend stays lit while the accessory is off.

The five-pin switch shown has two lighting functions:

• An upper indicator that illuminates when the accessory is on

• A lower backlight that can connect to the vehicle's running-light or dash-light circuit

The two lamp circuits keep the switch legend visible at night without turning on the accessory.

Example terminal functions

Some five-pin switches internally use a lamp-negative connection instead of providing two separate lamp terminals. Follow the exact diagram supplied with the switch.

Wiring steps

1. Disconnect the battery negative terminal.

2. Run a fused positive feed to the POWER terminal.

3. Connect ACC or LOAD to the accessory's positive lead.

4. For a relay-controlled load, connect ACC or LOAD to the relay's positive coil terminal instead.

5. Connect IND NEG to the vehicle negative return or chassis ground.

6. Connect DASH POS to the running-light or dash-light circuit.

7. Connect DASH NEG to the negative return.

8. Leave the dash-lamp terminals disconnected if backlighting is not required.

9. Reconnect the battery and test the accessory, ON indicator, and dash lamp separately.

Do not connect both dash-lamp terminals to the running-light positive conductor. One side of the lamp must connect to its designated negative return unless the manufacturer's diagram shows a different internal arrangement.

How to Wire a 4-Pin Rocker Switch for 240V AC

Typical use: 240V equipment that must disconnect both ungrounded conductors, such as a shop compressor or a machine tool.

People often search for a "220V rocker switch," but North American equipment is typically supplied at a nominal 240V. The example shown here is a non-illuminated, four-terminal DPST switch that disconnects both ungrounded conductors.

A four-pin rocker is not automatically a DPST switch. Four-terminal housings may also be used for other contact and lamp arrangements. Use this section only when the switch schematic confirms two mechanically linked poles.

Example terminal functions

A standard North American 240V load normally uses L1 and L2 rather than phase and neutral. A neutral may be present when equipment also requires a 120V line-to-neutral supply, but it must be connected according to the equipment diagram.

Wiring steps

1. De-energize the circuit at its disconnect or circuit breaker.

2. Verify the absence of voltage with an appropriate tester.

3. Connect incoming L1 and L2 to the terminals designated as LINE.

4. Connect the corresponding LOAD terminals to the equipment.

5. Run the equipment grounding conductor directly to the equipment grounding point.

6. Never interrupt the equipment grounding conductor with the rocker switch.

7. Connect any neutral conductor according to the equipment manufacturer's diagram.

8. Reassemble the equipment before restoring power.

Automotive primary wire is not suitable for a 120V or 240V branch circuit. Permanently installed AC wiring must use listed conductors and wiring methods appropriate for the equipment, enclosure, circuit rating, and applicable electrical code.

Dual-rated THHN/THWN-2 building wire is suitable for wet or dry locations at up to 90°C, subject to conductor markings, terminal temperature limits, installation conditions, and applicable code requirements.

AC wiring presents a serious shock and fire risk. Permanent installations should be completed or checked by a qualified electrician.

How to Wire the 7-Pin Winch Rocker Shown in the Diagram

Typical use: a load that runs in two directions under momentary control, such as a winch or a linear actuator.

The seven-terminal switch in this guide is a dual-pole, momentary ON-OFF-ON control switch. It is intended to send low-current IN and OUT signals to a winch solenoid or contactor pack.

It does not carry the winch motor current.

When released, the momentary rocker returns to the center OFF position. Other seven-terminal switches may use different contact pairings, so the following assignments apply only to the switch shown.

Example terminal functions

In one direction, terminals 1 and 2 close while terminals 4 and 5 close. In the other direction, terminals 2 and 3 close while terminals 5 and 6 close.

Winch-control wiring steps

1. Disconnect the battery and isolate the winch power circuit.

2. Confirm the switch contact arrangement with a multimeter.

3. Run a fused positive control feed to terminals 2 and 5.

4. Connect terminals 3 and 6 to the solenoid or contactor's IN trigger connections.

5. Connect terminals 1 and 4 to the OUT trigger connections.

6. Connect terminal 7 to the appropriate negative return if the switch uses the lamp arrangement shown.

7. Reconnect power.

8. Test both directions without a load before performing a full pull.

The correct IN and OUT pairing depends on the winch contactor. If the switch operates in the opposite direction from its legend, verify the trigger connections against the winch manufacturer's schematic rather than changing high-current motor cables at random.

Contura-style switches are available with multiple internal contact and illumination arrangements. "Contura II" primarily describes an actuator style and does not establish a universal seven-terminal pinout.

When to Add a Relay

Use a relay when:

• The load's maximum operating current exceeds the switch's applicable DC rating

• Motor, compressor, incandescent lamp, or other startup current may exceed the contact rating

• The equipment manufacturer requires relay control

• You want to keep the high-current cable run short

• The switch is intended only to provide a control signal

Do not base the decision on a universal percentage of the switch rating. Check the rating at the actual voltage and load type. A switch may have different ratings for resistive, inductive, lamp, AC, and DC loads. Carling's V-Series, for example, lists different contact limits depending on voltage and circuit selection.

Standard automotive relay connections

When the rocker switch energizes the relay coil between terminals 85 and 86, the relay connects terminal 30 to terminal 87.

Always check the diagram printed on the relay. Coil polarity is especially important when the relay contains a suppression diode. Reverse polarity can damage the suppression device and the connected circuit.

Wire Gauge for 12V Rocker-Switch Circuits

Voltage drop has a noticeable effect in 12V systems. Excessive resistance leaves accessories underpowered.

Use the table below as a starting point for typical copper accessory circuits.

Total circuit length is the sum of the positive conductor and the negative return conductor.

The table does not replace a project-specific calculation. Check:

• Maximum continuous current

• Motor or lamp startup current

• Permitted voltage drop

• Ambient temperature

• Number of bundled conductors

• Connector and terminal ratings

• Manufacturer instructions

Wire in a tightly packed harness may require derating. SAE automotive conductors may also contain less copper than an equivalently numbered AWG conductor, so confirm the actual construction instead of selecting wire by gauge marking alone.

Use the equipment manufacturer's sizing chart for winches, starter circuits, large compressors, and other high-current equipment.

Fuse Sizing for Rocker-Switch Circuits

The fuse protects the conductor and downstream circuit from excessive current. It is not selected solely from the accessory's normal operating current.

Choose a fuse that:

• Carries the maximum expected operating current

• Tolerates normal startup or inrush current

• Does not exceed the allowable rating of the smallest wire, terminal, connector, or other protected component

• Matches the equipment manufacturer's recommendation

• Uses an appropriate time-current characteristic for the load

Install the fuse as close to the battery or other power source as possible. In marine DC systems, per ABYC guidance, overcurrent protection is generally installed within 7 inches of the source connection, with defined exceptions.

Use a sealed fuse holder in engine bays, marine installations, and other areas exposed to moisture or spray.

Never increase the fuse size to stop repeated fuse failures without first finding the overload, inrush, wiring, or equipment problem.

Choosing Cable for Rocker-Switch Circuits

Match the cable to the environment before selecting the final conductor size.

Automotive primary wire

Automotive primary wire uses flexible stranded conductors and insulation designed for vehicle harnesses.

GPT is a common general-purpose PVC automotive wire, while GXL and TXL use cross-linked polyethene insulation. Exact temperature, chemical-resistance, and voltage ratings depend on the individual product and manufacturer.

Use GXL, SXL, or another appropriately rated construction in higher-temperature areas, but maintain clearance from exhaust components, turbochargers, and other direct heat sources. Insulation type does not eliminate the need for correct routing and mechanical protection.

Marine wire

Marine wire uses tinned copper strands to reduce corrosion in wet and salt-laden environments.

Look for:

• UL 1426 boat-cable listing

• Tinned copper throughout the conductor

• Flexible stranding suitable for vibration

• Insulation rated for the installation environment

• Terminals and heat shrink suitable for marine use

Use red for DC positive. Yellow is commonly preferred for DC negative on boats because it reduces the chance of confusing a black DC-negative conductor with a black AC-hot conductor.

Connect accessory negative conductors to the vessel's DC negative bus. Do not treat a metal hull as the equivalent of a vehicle chassis return.

Browse marine wire and cable for UL 1426 tinned conductors and Anchor marine-grade boat cable for larger feeder runs.

Battery cable for high-current loads

A rocker switch may control a winch or compressor without carrying its main operating current. The high-current path runs through the battery cable between the battery, fuse or circuit breaker, contactor, and motor.

Size battery cable according to:

• The equipment manufacturer's current rating

• Maximum current under load

• Total cable length

• Acceptable voltage drop

• Ambient temperature and routing

Use tinned battery cable in marine environments and where road salt or persistent moisture is present.

Wire for AC rocker-switch circuits

Do not use automotive primary wire for a 120V or 240V branch circuit, regardless of gauge.

AC equipment wiring may require THHN/THWN-2, flexible cord, machine-tool wire, appliance wiring material, or another listed construction depending on the equipment and installation method.

THHN is intended for dry locations, while dual-rated THHN/THWN-2 is suitable for wet or dry locations at up to 90°C, with a 75°C limit where specified for oil exposure.

Follow the equipment listing, conductor markings, terminal temperature ratings, and applicable code.

Terminals and Crimps

The termination is often the highest-resistance point in a rocker-switch circuit.

• Most full-size rocker switches use 0.250-inch quick-connect terminals.

• Compact switches commonly use 0.187-inch terminals.

• Match the terminal blade size and barrel size to the switch and conductor.

• Use a ratcheting crimp tool with the correct die.

• Perform a pull test after crimping.

• Protect moisture-exposed connections with adhesive-lined heat shrink.

• Support the conductor so it cannot repeatedly flex at the terminal.

• Do not rely on solder alone for vibration-prone wiring.

Carling's full-size V-Series switches use 0.250-inch quick-connect terminals as a standard option, although other terminations are available.

Nassau National Cable also supplies terminals, lugs, connectors, and heat-shrink products for vehicle, marine, and equipment wiring.

Quick Cable Reference

• Interior switch panel, low-current load: TWP or GPT, commonly 18 to 16 AWG

• Engine-bay accessory: GXL or SXL, sized to current and length

• Light bar controlled through a relay: Automotive primary wire sized separately for the trigger and load circuits

• Boat accessory circuit: UL 1426 tinned marine wire

• Winch-solenoid trigger: GXL or tinned marine wire

• Winch motor and battery leads: Battery cable sized from the winch manufacturer's chart

• 120V or 240V AC equipment: Listed building or equipment wire suitable for the installation

Application Notes

Boats

Return accessory current through the vessel's DC negative wiring and negative bus. Keep DC-negative, AC-grounding, and bonding terminology distinct.

Use sealed terminals, tinned conductors, and ignition-protected components where required. Follow the diagrams from the vessel and equipment manufacturers.

Cars and trucks

Route accessory wiring away from:

• Steering shafts and pedals

• Exhaust components

• Sharp sheet-metal edges

• Door hinges

• Airbags and seat-belt pretensioner wiring

• Moving suspension and drivetrain parts

Install a suitable grommet or bulkhead fitting wherever wiring passes through sheet metal.

Multiple-switch panels

A switch panel may use a common positive bus and a common negative bus, but the panel feeder and individual branches must be protected correctly.

A main panel fuse protects the feeder. Smaller branch wiring may require separate protection sized to the smallest conductor and connected component in each branch.

Rock lights and LED strips

Calculate the total current of the complete lighting set. A three-pin rocker can control the load directly only when the switch's applicable DC rating safely exceeds the operating and startup current.

Observe LED polarity and use a relay when required by the light manufacturer.

Troubleshooting a Rocker Switch

Disconnect power immediately if the switch, terminal, fuse holder, or conductor becomes hot.

For a dead circuit, check the system in order:

1. Source voltage

2. Fuse continuity

3. Voltage at the switch input

4. Switch continuity

5. Voltage at the switch output

6. Relay operation, if used

7. Load connection

8. Negative return path

Safety Checklist

• Isolate the battery or AC supply before starting.

• Verify terminal functions instead of relying on pin count.

• Use a fuse or circuit breaker at the power source.

• Size conductors for current, length, temperature, and voltage drop.

• Keep DC and AC wiring physically separated.

• Protect wiring from heat, abrasion, moisture, and moving parts.

• Use sealed terminals in marine and engine-bay locations.

• Never switch an equipment grounding conductor.

• Use a relay or contactor when the switch is not rated for the load.

• Hire a qualified electrician for permanently installed AC wiring.

Frequently Asked Questions

How do you wire a 2-pin rocker switch?

A two-pin on/off switch normally has one input and one switched output. Connect fused positive to one terminal and the load's positive lead to the other.

A basic mechanical SPST switch is generally not polarity-sensitive, but you must still verify the switch rating and schematic.

What is the difference between a 3-pin and a 4-pin rocker switch?

There is no universal difference based on pin count alone.

A three-pin switch may be an illuminated SPST switch or an SPDT switch. A four-pin switch may be DPST, illuminated SPST, or another configuration. Identify the circuit from the manufacturer's schematic.

How do you wire a 3-prong rocker switch?

For the illuminated three-pin design shown in this guide, connect fused positive to POWER, the accessory to LOAD, and the lamp-negative terminal to the system negative.

Do not apply this layout to an unverified three-prong switch.

How do you wire a 5-pin rocker switch?

The five-pin switch shown uses two switching terminals, a negative connection for the ON indicator, and positive and negative connections for the separate dash backlight.

Other five-pin switches may share lamp connections internally, so verify the pinout before wiring.

How do you wire a 6-pin rocker switch?

Many six-terminal rocker switches use a DPDT arrangement with three terminals per pole, but the center position and contact pairings vary.

Use a multimeter to identify the two common terminals and determine which contacts close in each rocker position.

How do you wire an 8-pin rocker switch?

Eight-terminal switches may combine switching contacts with one or more lamp circuits. Some Contura switches use an eight-terminal base even when not every position is populated.

Follow the part-number-specific contact and illumination diagrams.

Do I need a relay for a rocker switch?

Use a relay when the load's continuous or startup current exceeds the switch's applicable DC rating, when the manufacturer specifies relay control, or when keeping high-current wiring away from the dashboard would improve the installation.

Small indicator lights and low-current electronics may not require one. Large light bars, motors, pumps, and compressors often do.

Why does my lighted rocker switch remain dimly lit?

A dim glow with the switch off may result from an incorrect lamp connection or a small backfeed through an LED driver, controller, relay module, or electronic load.

Verify the complete switch pinout before moving any wire to ground.

Can the same rocker switch be used for 12V DC and 120V AC?

Only when the switch is explicitly rated for both the voltage and the applicable current and load type.

Do not assume that an AC rating automatically permits the same current on DC. Switch manufacturers distinguish between AC-only, DC, and dual AC/DC ratings.

Why does a rocker switch need a ground connection?

The switching contacts often do not need a ground or negative connection. The additional terminal usually provides a negative return for a built-in indicator or backlight.

An unlighted two-pin switch normally interrupts only the positive or line conductor.

Source Your Wire From Nassau National Cable

Nassau National Cable stocks automotive wire, marine wire and cable, battery cable, and connectors and accessories for rocker-switch and accessory circuits.