55021 Littelfuse 55021 Toggle Switch (SPDT, Momentary) – Heavy-Duty Series

Littelfuse 55021 Toggle Switch Overview for harsh-environment control

The Littelfuse 55021 is a heavy-duty, panel-mount toggle switch built for demanding vehicle and equipment environments. As part of Littelfuse’s Standard Heavy Duty Toggle Switch Series, it combines a robust mechanical design with corrosion-resistant silver contacts and a classic, glove-friendly metal actuator. The 55021 uses a Single-Pole, Double-Throw (SPDT) mechanism with a “Momentary On – Off – Momentary On” detent pattern, making it ideal wherever an operator needs spring-return control in both directions—think motor reversing, hoist up/down, or extend/retract commands.

The device mounts through a standard 15/32 in (≈11.9 mm) panel hole using a nickel-plated brass face nut, which provides an excellent mechanical grip and a clean, finished look on metal or composite panels. Electrical connections are fast and field-serviceable via three screw terminals, a preferred style in fleet maintenance because it accommodates ring or spade lugs and enables quick swap-outs.

At the heart of the series is Littelfuse’s focus on longevity and reliability. The switch body is a black, rugged plastic with a plated steel cap that shields the mechanism, while the nickel-plated brass actuator (standard handle length ~17.46 mm) delivers a precise feel and repeatable momentary action. For the whole Standard Heavy Duty family, Littelfuse specifies DC ratings up to 10 A at 36 V (with higher current at lower voltages), giving designers predictable performance on 12/24/36 V vehicle electrical systems.

Specifications (Littelfuse 55021)

Notes on ratings: The datasheet for the Standard Heavy Duty Toggle Switch family provides DC ratings up to 10 A at 36 V, 15 A at 24 V, and 25 A at 12 V. Select fusing and wiring according to your system voltage and applicable standards.

Detailed Description

Heavy-duty construction for uptime

Everything about the 55021’s build serves longevity in real-world fleets. The black plastic body is capped with plated steel to resist impact and abrasion, while the silver contacts fight corrosion in damp, dirty cabins or enclosures. The metal actuator gives operators a confident grip—even with gloves—without the wobble or vague detents that make precise control difficult. The spring-return hardware in both directions (momentary both up and down) snaps the lever back to center as soon as the operator releases it, reducing the risk of leaving a circuit engaged unintentionally and helping meet safety expectations for “dead-man” style operation.

Simple panel mounting

A single 15/32 in (≈11.9 mm) round hole is all that’s required. The nickel-plated brass face nut tightens down securely on painted steel, aluminum, or plastic panels, distributing clamp force to resist loosening from vibration. The standard handle length (~17.46 mm above the panel) balances leverage and clearance so the switch is easy to flick yet unlikely to snag.

Service-friendly screw terminals

The 55021 uses three screw terminals compatible with ring/spade lugs—ideal for field service and modifications. Compared with solder lugs or PCB pins, screw terminals speed replacement: loosen, swap, tighten. This is a practical advantage for commercial vehicles and equipment where downtime is costly and wiring looms vary between upfits.

Flexible DC performance across 12/24/36 V systems

Within the Standard Heavy Duty series, Littelfuse publishes DC ratings suited to the most common mobile power architectures: 25 A at 12 V, 15 A at 24 V, and 10 A at 36 V. That means one switch family can cover light trucks and off-highway machines at 12 V, buses and some materials-handling gear at 24 V, and specialty 36 V platforms. It simplifies procurement while keeping compliance straightforward. As always, protect circuits with appropriate fuses or breakers.

The right detents for bidirectional control

“Momentary On – Off – Momentary On” detents are the go-to choice for reversing or jogging actions. Wire the common to supply and the two throws to the A/B inputs of your load (or to the forward/reverse coil of a contactor), and the lever returns to Off when released. This improves operator safety and repeatability in short, deliberate actuations. Typical examples include:

• Winch in/out

• Hydraulic extend/retract (via valve solenoids)

• Lift-gate raise/lower

• Vibratory feeders jog control

• Wiper or auxiliary motor jog

The 55021’s tactile springing and metal lever deliver clear feedback as the operator crosses the neutral position, further reducing accidental long engagements.

Family breadth and drop-in alternates

If you need the same form factor but a different function, the Standard Heavy Duty family includes SPST, SPDT, DPDT, and even 4PDT options, plus alternate detents (On-Off, On-On, On-Off-On, and Momentary variants). There are leaded and sealed versions, long-handle options, and different termination styles. For example, the 55021-07 variant adds a weather-resistant PVC-coated housing and blunt-cut leads for environments where screw terminals are impractical. This breadth allows platform teams to standardize panel cutouts and actuation feel while tailoring circuitry per function.

Applications

• Construction equipment – loader auxiliary circuits, beacon control through interposing relays, or jog functions for actuators.

• Agricultural machinery – auger jog, chute adjust, or reel extend/retract where a spring-return control is preferred.

• Material-handling equipment – lift-gate raise/lower, conveyor jog, dock leveler actuation.

• Commercial vehicles & specialty trucks – PTO auxiliary controls, winch in/out, snow-equipment functions via solenoids.

These are exactly the domains for which Littelfuse positions the Standard Heavy Duty Toggle Switches line, owing to its rugged mechanics and corrosion-resistant contact system.

Three quick highlights

• True heavy-duty build – silver contacts, plated-steel cap, and metal actuator for long service life in harsh cabins.

• Operator-safe control – momentary action in both directions springs back to center to help prevent unintended run-on.

• Fleet-friendly service – 3 screw terminals and a standard 15/32 in panel hole speed installation and replacement.

Design & Selection Notes

1. Panel & spacing: The 17.46 mm standard handle provides comfortable leverage. Allow room above the lever for gloved operation and below the panel for terminal clearance and lug bend radius.

2. Circuit protection: Size upstream fusing to match your load and the series’ voltage rating table (e.g., 10 A at 36 V DC). De-rate appropriately for ambient temperature, duty cycle, and inductive loads.

3. Inductive loads: For motors, solenoids, or relays, include flyback suppression (diodes, TVS, or RC snubbers) to minimize arcing and extend contact life. (General best practice.)

4. Variants: If exposure to washdown or weather is expected, consider the 55021-07 leaded, weather-resistant version from the same family.

5. Kitting & packaging: Choose bulk (55021), boxed (55021-BX), or blister (55021-BP) depending on service or retail requirements.

Why choose Littelfuse for heavy-duty toggles?

Littelfuse is a recognized leader in commercial vehicle electrical protection and control. The Standard Heavy Duty Toggle Switch family is engineered for universal fit and long lifecycle across equipment platforms. Consistent mounting (15/32 in hole), consistent tactile feel, and a wide range of circuits let you build intuitive panels without juggling disparate footprints or unreliable off-brand parts. Datasheets and 2D prints are readily available to speed up CAD integration and documentation.

What’s in the box / order codes

Here are the Littelfuse 55021 series models I can confirm from official product pages and 2D print documents:

For sealed/leaded weather-resistant builds, see 55021-07 and its packaging codes. Full ordering tables are presented on page 2 of the series datasheet.

If you’re standardizing panels across multiple functions, combine the 55021 with other part numbers in the same family (e.g., On-Off or On-On versions) to keep ergonomics and hole sizes consistent while matching the required circuitry. Littelfuse also provides application guides, 2D drawings, and related resources to streamline your integration.

Source: Littelfuse “Standard Heavy Duty Toggle Switches” datasheet (features, mounting, ratings, ordering table for 55021, and application domains).