21SN04-275A — Low Pressure Oil Switch Repair & Overhaul

Component Overview

A low pressure oil switch is a pressure-sensing switch that detects when engine or system oil pressure falls below a safe threshold, actuating electrical contacts to trigger a cockpit warning of impending lubrication loss. It typically uses a diaphragm or piston referenced against a calibrated spring to close or open contacts at a defined low-pressure setpoint, providing an early indication of pump failure, leakage, or oil starvation. Within the sensors and switches group it is a protective monitoring device for the lubrication system. Repair and overhaul are driven by diaphragm or piston fatigue, calibration and setpoint drift, spring relaxation, electrical contact wear and pitting, port seal leakage, corrosion, and contamination that cause inaccurate actuation, nuisance warnings, or failure to signal a genuine low-pressure condition.

Aircraft Application

Part number 21SN04-275A (Low Pressure Oil 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 21SN04-275A 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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Frequently Asked Questions