4-Pin Rocker Switch Wiring Diagram: How to Wire a 4-Pin DPST or Illuminated Switch

4-Pin Rocker Switch Wiring Diagram: How to Wire a 4-Pin DPST or Illuminated Switch — interactive diagram. Open it in the editor to customise components and wiring.

This is a free printable 4 pin rocker switch wiring diagram: download the diagram as SVG or open it and print to paper or PDF.

A 4-pin rocker switch wiring diagram shows how the four terminals — which typically form a double-pole single-throw (DPST) or a single-pole switch with an indicator lamp — connect to a load, power supply, and indicator lamp circuit.

Rocker switches with four pins are very common in automotive accessories, marine fittings, and 12 V/24 V DC control panels. The four-pin configuration is used for two different switch types, and understanding which type you have is essential before wiring.

The first type is a DPST (double-pole single-throw) rocker switch. The four pins form two independent switch poles that open and close simultaneously. Pins 1 and 2 are the input and output of the first pole; pins 3 and 4 are the input and output of the second pole. Pressing the rocker connects both poles simultaneously. DPST switches are used when both the positive and negative (or live and neutral) conductors of a circuit must be interrupted together — common in marine applications for safety isolation, and in 24 V systems where both supply rails are switched.

The second type is a single-pole switch with a built-in pilot lamp (illuminated rocker switch). In this case, two of the four pins connect to the main switch contacts (the load circuit), and the other two pins connect the internal indicator lamp. The lamp circuit is typically: one lamp pin connects to the supply positive (to keep the lamp lit whenever the supply is present and the rocker is off), and the other lamp pin to the switch output (so the lamp indicates whether the load is energised). In some illuminated switch designs, the lamp is wired to illuminate only when the switch is on; in others it illuminates when the switch is off as a reminder.

Pin numbering or labelling varies between manufacturers. Common conventions for a 4-pin illuminated switch: pins 1 and 2 are the main switch contacts; pins 3 and 4 are the lamp terminals. For a DPST: pins 1 and 3 may be the two inputs (both connected to supply positive), and pins 2 and 4 are the two outputs to respective loads.

Always confirm the pinout of the specific switch being used with a multimeter in continuity mode before wiring — or use the manufacturer's data sheet.

How to wire 4 pin rocker switch wiring diagram

Identify the switch type and pin layout Determine if the switch is a DPST type or an illuminated single-pole type. Use a multimeter in continuity mode to map which pins connect to the main contacts and which (if any) to the lamp. Note which pin position corresponds to which terminal number on the switch body.
Plan the circuit For a DPST switch: identify which two conductors need to be switched simultaneously and connect the supply side to the input pins (1 and 3) and the load side to the output pins (2 and 4). For an illuminated single-pole switch: identify the main contact pins and lamp pins, then plan whether the lamp should indicate 'on' or 'off' state.
Connect the main switch contact pins For a DPST: connect the positive supply conductor to main contact input pin 1, the negative supply conductor to main contact input pin 3. Connect the load positive conductor to output pin 2 and load negative conductor to output pin 4. For a single-pole illuminated type: connect supply positive to pin 1, switched output to pin 2.
Connect the lamp circuit (illuminated type only) To make the lamp illuminate when the switch is ON: connect the lamp supply pin to the supply positive and the lamp return pin to the switched output side of the main contact. When the switch closes, current flows through the lamp. To make the lamp illuminate when the switch is OFF: connect the lamp supply pin to the supply positive and the lamp return pin to ground/supply negative.
Add a protective fuse to the load circuit Install an appropriately rated fuse or circuit breaker in the positive supply line feeding the switch. The fuse rating should match the cable ampacity and the load current — not simply the maximum switch contact rating. The switch's contact rating is the maximum it can handle, not the correct fuse value.
Secure all connections and test Use crimp terminals or solder-and-heat-shrink connections — bare twisted wire pushed onto bare spade terminals corrodes rapidly and creates high resistance. Apply power and verify the load operates when the switch is pressed. Verify the lamp illuminates in the intended state (on or off). Check that no excess heat develops in the switch or wiring.

Specifications

Common contact configurations (4-pin)	DPST (double-pole single-throw) or illuminated SPST with separate lamp pins
Typical automotive rocker contact rating	10–30 A at 12 V DC (verify data sheet for specific switch)
Typical spade terminal size on automotive rocker switches	4.8 mm (3/16 in) or 6.3 mm (1/4 in) blade width
Standard mounting hole size (large automotive rocker)	29 mm × 22 mm (commonly used for ARB, Narva, and similar panel switches)
Standard mounting hole size (small automotive rocker)	20 mm × 13 mm (commonly used for smaller 12 V accessories)
Typical indicator lamp voltage (automotive type)	12 V DC or 24 V DC (match to system voltage)

Safety warnings

Disconnect the vehicle battery negative terminal before wiring any switch into an automotive circuit. This prevents accidental short-circuits and protects vehicle electronics. This diagram is illustrative and reference-only — consult local vehicle modification regulations and wiring codes.
Always fuse the positive supply line feeding the switch. The fuse must be rated for the load current and positioned as close to the supply source (battery or fuse box) as practical.
Do not exceed the switch's rated contact current and voltage. Overloading the contacts causes arcing, contact welding, and switch failure — potentially with the load permanently energised.
Ensure all spade terminal connections are fully seated and crimped. A loose connection on a switched circuit can arc, generating localised heat that risks fire in surrounding materials.
For marine installations, use marine-rated switches and tinned copper wiring. Standard automotive switches used in saltwater environments corrode rapidly and can seize in the on or off position.

Tools needed

Digital multimeter with continuity/resistance mode (for pin identification)
Wire strippers for the cable gauge used
Ratchet crimp tool for spade terminals
Panel punch or step drill for mounting hole (if fitting in a panel)
Insulation tape or heat-shrink tubing
Test light or LED tester for circuit verification

Common mistakes

Connecting wires to the wrong pins because pin 1/2/3/4 numbering varies between manufacturers — always verify with a multimeter rather than assuming.
Not fusing the circuit — a switch is not a protection device and will not protect wiring from a short-circuit downstream of it.
Using an undersized switch — selecting a decorative rocker switch rated for only 5 A on a 15 A lighting or pump circuit causes contact burning and eventual failure.
Using bare twisted wire pushed onto spade tabs without proper crimped terminals — vibration and corrosion create high-resistance connections that heat up.
Wiring the lamp circuit to the same voltage but across the supply directly (both lamp pins to supply) — the lamp stays permanently on regardless of switch position.
Forgetting to account for the switch's body depth when mounting in a panel — insufficient clearance prevents the rocker from operating freely.

Troubleshooting

Switch clicks but load does not operate: Cause: No supply voltage reaching the switch input pin, blown fuse, or broken connection at the load Fix: Measure supply voltage at the switch input contact pin with the switch pressed. If no voltage, check the fuse and trace back to the supply. If voltage is present at the input but not at the output pin, the switch contacts have failed or there is no internal connection — test with a multimeter in continuity mode.
Indicator lamp does not illuminate: Cause: Lamp pins not connected, lamp burned out, or lamp connected across the wrong terminal pair Fix: Verify the lamp pin connections using the switch data sheet. Apply supply voltage directly across the lamp pins — if the lamp does not illuminate, the internal lamp has failed and the switch should be replaced (most rocker switch lamps are not individually replaceable).
Switch operates load but load does not turn off completely: Cause: The switch is a DPST type and only one pole is connected — the load has a secondary current path via the unconnected pole Fix: For a DPST switch, ensure both poles are correctly wired. Alternatively, if only one pole is needed, confirm the circuit does not have any alternate current path that bypasses the switch contact.

Frequently asked questions

How do I identify which pins are the switch contacts and which are the lamp on a 4-pin illuminated rocker switch?

Use a multimeter in resistance/continuity mode with the switch disconnected from the circuit. With the rocker in the off position, locate the two pins that show continuity with the rocker pressed — those are the main switch contacts. The remaining two pins are the lamp circuit. Apply low voltage across various pin combinations to observe when the lamp illuminates.

Can the indicator lamp in a 4-pin switch operate on a different voltage from the main switch circuit?

Yes, if the lamp circuit is fully independent (as it is in a properly designed 4-pin switch). The two lamp pins can be connected to any voltage within the lamp's rated range, independently of what the main switch contacts are switching. However, in many common automotive illuminated rockers, the lamp is internally rated for the same voltage as the intended application — do not exceed it.

What does DPST mean for a rocker switch?

DPST stands for double-pole single-throw. The switch has two independent sets of contacts (poles) that both open and close together when the rocker is operated. It has one position for on and one for off. A DPST switch can simultaneously disconnect both conductors of a two-wire circuit, which is required in marine wiring practice to isolate loads fully from the battery.

Does it matter which way round the two main switch contact pins are connected?

For a simple on/off DPST or SPST switch, the two switch contact pins are equivalent — current can flow in either direction through the switch. However, for an illuminated switch where the lamp is wired via the switch contacts in some designs, the orientation may affect whether the lamp is on when the switch is on or off. Check the data sheet for the intended lamp-wiring orientation.

Why does my illuminated rocker switch lamp stay on even when the switch is off?

This is often the intended design — an 'off' indicator lamp wired to glow when the switch is off, reminding the user that the switch is not active. If it is unintended, the lamp terminal may be connected to the permanent supply rail rather than the switched output rail. Trace the lamp pin wiring and compare with the switch data sheet.

Related diagrams

Free electrical calculators

Edit this diagram free in the online editor