Pollak 51-918 Master Disconnect Switch with Indexing Post – DPST, 180A Continuous

Overview

The Pollak 51-918 Master Disconnect Switch is a high-performance electrical safety solution designed for heavy-duty vehicles and equipment. Sharing the robust internal architecture of the popular 51-904, the 51-918 adds an integrated .25" diameter indexing post to prevent the switch from rotating or loosening in the mounting panel during use.

This DPST (Double Pole, Single Throw) switch is engineered to simultaneously disconnect both the battery and the alternator field circuit. This "field disconnect" feature is critical for modern charging systems, as it prevents the engine from continuing to run (and potentially damaging the alternator) once the battery circuit is cut.

Key Features

• Anti-Rotation Indexing Post: Includes a .25" diameter pin to ensure the switch remains perfectly aligned and won't spin during high-torque operation.

• Dual Circuit Control (DPST): Safely interrupts both the main battery power and the alternator/generator field circuit.

• Rugged Construction: Features a one-piece die-cast housing and heavy-duty silver-plated contacts for maximum conductivity and corrosion resistance.

• Weatherproof Protection: O-ring sealed at the base and mounting stem to lock out moisture, dust, and grime in harsh environments.

• High Amperage Capacity: Rated for 180 Amps continuous and a 1000 Amp intermittent in-rush.

Technical Specifications

• Part Number: 51-918 (also known as 51-918P / 51-918EP)

• Circuitry: DPST (Off-On)

• Voltage: 6V - 36V DC

• Rating: 180A Continuous / 1000A Intermittent (20 sec ON / 5 min OFF)

• Terminals: Two 3/8"-24 Copper Alloy Studs (Battery); Two #10-32 Studs (Alternator)

• Mounting Stem: 3/4" Diameter, 1/2" Long

• Alignment Feature: .25" Diameter Indexing Post

Recommended Applications

• Heavy-Duty Trucks: Prevents battery drain and adds a layer of safety during emergency repairs.

• Emergency Vehicles: Ideal for fire trucks and ambulances requiring reliable field circuit isolation.

• Marine & Off-Road: Built to withstand vibration and moisture in demanding offshore or trail environments.

• Agricultural Equipment: Provides a secure lockout for tractors and combines during storage.