165-4026 (CAT) 24V Power / Starter Relay (Magnetic Switch)

Genuine CAT High-Power Master Power Relay, used to control the machine's main power supply, starter circuit, and battery protection functions.

I. Key Specifications

Part Number: 165-4026 / 1654026

Type: 24V DC Electromagnetic Power Relay / Starter Relay (Magnetic Switch)

Voltage: 24V DC (Standard heavy equipment voltage; 12V is not supported)

Contact Capacity: High Current (200A+); controls the machine's main power supply

Interface: 4 Large Terminals + 2-Pin Control Coil Connector

Mounting: Metal Bracket (Dual-tab / Single-tab)

Protection: Fully sealed; water-resistant, dustproof, oil-resistant, and vibration-resistant

Functions: Main power ON/OFF control, starter circuit protection, and prevention of battery drain

II. Applicable Models (Primarily CAT Excavators)

300 Series: 311B, 312B, 312C, 315C, 318C, 320A, 320B, 320C, 320D, 322C, 325C, 330C, 345B, 365B, etc.

Engines: 3064, 3066, 3116, 3126B, C6.4, C7, etc.

Others: Select loaders and bulldozers utilizing the same voltage electrical system

III. Replacements and Interchangeability

Direct OEM Replacement:

3T-0376 / 3T0376 (Fully interchangeable; identical specifications and mounting)

OEM Alternative Part Numbers:

165-4026X (Common aftermarket version)

W-1503-2 (Internal factory reference number)

⚠️ Important Note: A 24V high-current power relay *must* be used; standard low-power relays are not suitable replacements.

IV. Function and Failure Symptoms

Primary Function: The key switch controls the on/off status of the entire unit's main power supply.

It protects the starter motor, battery, and main wiring against overload and short circuits.

It completely cuts off power after engine shutdown, preventing battery drain.

Common Faults:

Failure to power on / Complete loss of power to the vehicle (burnt contacts, burnt-out coil)

Weak starting / Failure to start (poor contact, excessive voltage drop)

Battery leakage after engine shutdown (stuck relay contacts, failure to disconnect)