178-2345 (1782345) — Caterpillar Water-in-Fuel Sensor (Water Separator Level Sensor). Used to detect accumulated water within the fuel filter/water separator and trigger an alarm to protect the fuel system. I. Core Basic Information

Part Number: 178-2345 (1782345)

Type: Capacitive Active Fluid Level Sensor (Non-float type; no moving parts)

Brand: Caterpillar

Function: Monitors water content in the fuel within the fuel-water separator; outputs a switch signal when the water level exceeds the limit, triggering the dashboard water-in-fuel warning light to alert the operator to drain the system.

II. Key Technical Specifications

Electrical: 4-pin DT waterproof connector; requires external 12V/24V power supply.

Thread Specification: 9/16"-18 SAE O-ring (American fine thread with O-ring seal).

Material: Probe constructed from polypropylene plastic; resistant to fuel, water, and corrosion.

Harness Length: 24 inches (approx. 61 cm).

Operating Temperature: -40°C to +125°C; suitable for the harsh operating conditions typical of heavy construction machinery.

Output Logic: Ground-type (Sink to Ground) or High-Side Switching.

III. Primary Compatible Engines

3066, C4.2, C6.4, C7, C9, C11, C13, C15, C18

3126, 3176C, 3406E, 3412E, and other electronically controlled engines.

IV. Primary Compatible Equipment

Excavators (Most Common)

320C, 320D, 323D, 324D, 325D, 329D, 330C, 330D, 336D, 345D, 349D

Wheel Loaders / Dozers / Motor Graders

950G/H, 962G/H, 966G/H, 972G/H, 980G/H; D6R, D7R, D8T; 12H, 140H, 160H

Other Equipment

Off-Highway Trucks 785C/D, 793D/F; Compactors: CS-563E, CP-563E; Paver: AP-655D

V. Replacement Models

239-6510, 272-4772 (Direct functional replacements; upgraded part numbers for certain machine models)

178-2334, 255-2928 (Common OEM replacement numbers)

VII. Common Faults and Replacement Guidelines

Fault Symptoms

Water separator has been drained, but the warning light remains illuminated (Sensor short circuit / stuck contact)

Water separator is full, but the warning light does not illuminate (Sensor open circuit / failure)

ECU reports a fault with the fuel-in-water sensor (e.g., codes P0467, P0468)

Replacement Guidelines

Perform this procedure after shutting down the engine; first, open the bottom drain valve to completely drain any accumulated water.

Disconnect the sensor connector plug, then use a wrench to unscrew and remove the old sensor.

Clean the mounting bore, install a new O-ring (Part No. 214-7568), and apply a small amount of sealant.

Tighten the new sensor to the specified torque (approximately 20–25 N·m).

Reconnect the plug, start the engine, and verify that the warning function operates correctly.

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