Temperature Sensors & Switches Repair & Overhaul

Temperature sensors and switches are the thermal nervous system of an aircraft's environmental control, pneumatic, and engine bleed circuits. Whether installed as a duct temperature sensor monitoring conditioned air, a fan air temperature sensor feeding the air conditioning packs, a pneumatic or manifold temperature sensor protecting downstream ducting, or a discrete overtemperature switch that trips at a fixed limit, these devices give the controller the data it needs to modulate valves and the protection logic it needs to shut a system down before damage occurs.

Most analog sensing elements are resistance temperature detectors (RTDs) or thermistors, in which a calibrated change in electrical resistance tracks temperature. These elements are packaged into probes, low-limit temperature sensors, and fan/sensor unit assemblies, while overtemperature switches typically use a bimetallic or gas-filled element that opens or closes a contact set at a defined threshold. Because the resistance characteristic must stay within tight tolerance for the control loop to behave correctly, accuracy is everything.

In service, sensing elements drift as the resistance wire ages and as repeated thermal cycling stresses the element and its seals. Switch contacts wear, oxidize, or shift their setpoint, and connector and harness integrity degrades. Repair and overhaul restore calibrated accuracy, sound insulation resistance, and reliable switching so the unit again reports and protects within specification.

QTC overhauls temperature sensors and switches through a controlled MRO workflow. Each unit is inspected and tested as received, then disassembled so the sensing element, contacts, seals, and connector can be evaluated. Worn or out-of-tolerance RTD/thermistor elements and degraded switch contacts are replaced, insulation and bonding are restored, and the housing is cleaned and inspected for corrosion or damage.

The reassembled unit is then recalibrated against traceable reference standards. Resistance-versus-temperature characteristic, insulation resistance, and continuity are verified across the operating range, and overtemperature switches are checked for accurate setpoint and reliable make/break behavior. Once the unit meets its functional and accuracy requirements, it is certified and returned to service with the appropriate airworthiness documentation.