Universal diagnostic library

What the component does—and what proves it failed

A fault code identifies a detected condition, not an automatically failed part.

Exact identityDirect answerSafe checksEvidenceStop condition

Reviewed records

27 exact answers

Air-conditioner contactor: function, symptoms, testing boundary and repair difficulty

Air-conditioner contactor switches high-voltage power to compressor and fan. Related symptoms include outdoor unit silent, buzzing, chattering or running while off. Those symptoms do not prove the component failed: confirm thermostat demand and external disconnect/breaker state.

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Consumer-device lithium battery: function, symptoms, testing boundary and repair difficulty

Consumer-device lithium battery stores energy and supplies regulated power. Related symptoms include rapid drain, shutdown, charging refusal, swelling or heat. Those symptoms do not prove the component failed: separate software use and charger issues from physical warnings.

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Dishwasher circulation pump: function, symptoms, testing boundary and repair difficulty

Dishwasher circulation pump pressurizes wash water through spray arms. Related symptoms include fills without washing, weak spray, grinding or motor codes. Those symptoms do not prove the component failed: confirm fill, spray-arm movement and approved filter condition.

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Dishwasher drain pump: function, symptoms, testing boundary and repair difficulty

Dishwasher drain pump moves wash water to the household drain. Related symptoms include standing water, drain codes, humming or silence. Those symptoms do not prove the component failed: clean the approved filter and prove the air gap, disposal and hose.

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Dishwasher leak or float sensor: function, symptoms, testing boundary and repair difficulty

Dishwasher leak or float sensor stops filling or starts draining when water reaches an unsafe area. Related symptoms include leak/overflow codes, continuous drain or refusal to start. Those symptoms do not prove the component failed: turn water off and identify the actual leak before resetting.

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Dryer gas ignition system: function, symptoms, testing boundary and repair difficulty

Dryer gas ignition system ignites and controls the burner through interlocked safeties. Related symptoms include no heat, intermittent heat, clicking or gas odor. Those symptoms do not prove the component failed: verify airflow, gas supply position and observable ignition sequence.

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Dryer heating element: function, symptoms, testing boundary and repair difficulty

Dryer heating element converts electrical power into controlled heat. Related symptoms include no/weak heat, heater codes or heat continuing incorrectly. Those symptoms do not prove the component failed: prove airflow, cycle and supply voltage before internal testing.

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Dryer thermal fuse: function, symptoms, testing boundary and repair difficulty

Dryer thermal fuse opens a safety circuit after over-temperature. Related symptoms include no heat, no start or shutdown after overheating. Those symptoms do not prove the component failed: inspect vent airflow and installation before blaming the fuse.

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Furnace flame sensor: function, symptoms, testing boundary and repair difficulty

Furnace flame sensor proves burner flame so gas can remain on. Related symptoms include burners light then stop, ignition lockout or flame-sense code. Those symptoms do not prove the component failed: record the sequence and exact code before assuming contamination.

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Furnace pressure switch: function, symptoms, testing boundary and repair difficulty

Furnace pressure switch proves combustion-air and vent pressure before ignition. Related symptoms include inducer without ignition, pressure code or lockout. Those symptoms do not prove the component failed: inspect only exterior intake/exhaust blockage and condensate.

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Gas oven igniter: function, symptoms, testing boundary and repair difficulty

Gas oven igniter heats so the safety valve can release gas. Related symptoms include long preheat, no flame, delayed ignition or cycling. Those symptoms do not prove the component failed: observe from outside the sealed burner area and note delay/odor.

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Generator engine-speed sensing: function, symptoms, testing boundary and repair difficulty

Generator engine-speed sensing lets the controller verify cranking and running RPM. Related symptoms include RPM loss, under/overspeed or unexpected shutdown. Those symptoms do not prove the component failed: separate no-start from loaded shutdown and preserve history.

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HDMI signal path: function, symptoms, testing boundary and repair difficulty

HDMI signal path carries negotiated video, audio and control data. Related symptoms include no signal, black screen, flicker, missing HDR/4K120 or audio. Those symptoms do not prove the component failed: test one known-good cable directly before advanced settings.

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Heat-pump reversing valve: function, symptoms, testing boundary and repair difficulty

Heat-pump reversing valve changes refrigerant direction between heating and cooling. Related symptoms include heats in cooling, cools in heating or will not change modes. Those symptoms do not prove the component failed: prove thermostat configuration, outdoor operation and mode behavior.

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HVAC run/start capacitor: function, symptoms, testing boundary and repair difficulty

HVAC run/start capacitor supports motor starting and running. Related symptoms include humming, slow fan, protection trip or hot motor. Those symptoms do not prove the component failed: do not diagnose by appearance; qualified measurement is required.

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Oven temperature sensor: function, symptoms, testing boundary and repair difficulty

Oven temperature sensor reports cavity temperature to regulate heat. Related symptoms include sensor codes, large temperature error or early stop. Those symptoms do not prove the component failed: compare after full preheat and verify exact model/code.

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Printer pickup roller: function, symptoms, testing boundary and repair difficulty

Printer pickup roller separates and advances one sheet. Related symptoms include no pickup, misfeed, multiple sheets or tray jam codes. Those symptoms do not prove the component failed: verify paper, guides, media and accessible roller contamination.

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Refrigerator defrost system: function, symptoms, testing boundary and repair difficulty

Refrigerator defrost system clears evaporator frost using heater, sensor and control. Related symptoms include progressive warming, heavy frost, blocked airflow or defrost codes. Those symptoms do not prove the component failed: document frost and door sealing before manual defrost.

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Refrigerator evaporator fan: function, symptoms, testing boundary and repair difficulty

Refrigerator evaporator fan moves cold air across the evaporator and compartments. Related symptoms include freezer cold/fridge warm, fan noise or airflow codes. Those symptoms do not prove the component failed: confirm doors, vents and frost without removing powered panels.

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Refrigerator inverter and compressor: function, symptoms, testing boundary and repair difficulty

Refrigerator inverter and compressor compresses refrigerant while the inverter controls motor power. Related symptoms include no cooling, clicking, inverter codes or no compressor start. Those symptoms do not prove the component failed: prove power, controls, fans and temperatures; sound alone is insufficient.

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Standby-generator fuel supply: function, symptoms, testing boundary and repair difficulty

Standby-generator fuel supply delivers specified fuel type, pressure and volume. Related symptoms include overcrank, underspeed, RPM loss or loaded shutdown. Those symptoms do not prove the component failed: verify shutoff, LP level and supplier status; do not adjust pressure.

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Standby-generator starting battery: function, symptoms, testing boundary and repair difficulty

Standby-generator starting battery powers the controller and cranks the engine. Related symptoms include slow/no crank, battery warning or startup RPM alarm. Those symptoms do not prove the component failed: read controller status and inspect external terminals with the unit disabled.

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USB-C display path: function, symptoms, testing boundary and repair difficulty

USB-C display path negotiates power, data and optional video capabilities. Related symptoms include dock charges with no display, low resolution or intermittent monitor. Those symptoms do not prove the component failed: verify both ports and cable support video/power—not just USB-C shape.

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Washer door or lid lock: function, symptoms, testing boundary and repair difficulty

Washer door or lid lock proves the opening is closed before agitation or spin. Related symptoms include no start, repeated clicking, locked-after-drain or door codes. Those symptoms do not prove the component failed: remove fabric pressure, drain fully and inspect external alignment.

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Washer drain pump: function, symptoms, testing boundary and repair difficulty

Washer drain pump moves used water through the drain hose. Related symptoms include standing water, long-drain codes, humming or silence. Those symptoms do not prove the component failed: prove the household drain, hose and customer-accessible filter first.

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Washer water-inlet valve: function, symptoms, testing boundary and repair difficulty

Washer water-inlet valve opens hot and cold fill paths. Related symptoms include slow/no fill, wrong temperature, overfill or filling while off. Those symptoms do not prove the component failed: verify faucets, pressure, hoses and approved inlet screens.

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Washer water-level sensor: function, symptoms, testing boundary and repair difficulty

Washer water-level sensor reports tub water level. Related symptoms include overfill, no fill, level codes or stages that never advance. Those symptoms do not prove the component failed: compare actual level, drain-hose installation and suds.

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Structured depth, not empty permutations

Every published record carries a direct answer, scope, ordered fixes, risk notes and sources.

Device and manufacturer hubs share a consistent record system, but each answer carries the relevant controls, fault boundaries, consequences and official support entry point for that platform.

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