21SN04-417 — Oil Filter Differential Pressure Switch Repair & Overhaul

Component Overview

An oil filter differential pressure switch monitors the pressure drop across an engine or system oil filter, providing a warning or bypass indication when the filter becomes clogged with contaminants. It senses the difference between filter inlet and outlet pressure and actuates electrical contacts at a preset differential, alerting the crew or triggering maintenance action before flow is restricted or the bypass opens. Within the sensors and switches architecture it serves as a condition-monitoring device protecting the lubrication system. Repair and overhaul are driven by diaphragm or piston fatigue, calibration drift of the actuation setpoint, spring relaxation, contact wear and pitting, seal leakage between the pressure ports, and contamination that cause inaccurate switching, false indications, or failure to actuate at the specified differential.

Aircraft Application

Part number 21SN04-417 (Oil Filter Differential Pressure Switch) is installed on the Pratt & Whitney PW2000/4000. QTC supports operators and MROs servicing this platform with certified repair and overhaul.

Our Repair Capability

QTC repairs and overhauls 21SN04-417 to the original manufacturer's specifications under our FAA and EASA Part 145 approvals. Our team — including former OEM sensors & switches engineers — performs teardown, inspection, cleaning, component replacement, functional testing, and certification, returning a serviceable unit with the appropriate airworthiness release. We also develop repairs for rejected and beyond-economic-repair (BER) hardware.

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Related Parts

Other oil filter differential pressure switch part numbers we repair — view all Oil Filter Differential Pressure Switch parts →

Frequently Asked Questions