Universal diagnostic library
HVAC troubleshooting by system and observed state
Resolve equipment, model, thermostat demand and indicator before treating a safety control as failed.
Browse by platform
6 complete records in this directoryAir conditioner runs but does not cool the house
Prove thermostat demand, indoor airflow and outdoor-unit operation before considering refrigerant or electrical components.
Open record Furnaces · no heatFurnace runs or calls for heat but the house stays cold
Separate thermostat demand, household power, airflow, ignition and safety lockout before changing controls. A repeated ignition or limit fault requires service.
Open record Furnaces · cyclingFurnace starts and stops every few minutes
Short cycling can come from thermostat placement, restricted airflow, overheating protection, flame loss or sizing. Record run time and the fault light before cycling power.
Open record Heat pumps · auxiliary heatHeat pump auxiliary or emergency heat stays on
Auxiliary heat may be normal in cold weather, defrost or large temperature recovery. It is suspicious when it remains active in mild weather after setpoint is reached.
Open record Thermostats · powerThermostat screen is blank
A blank thermostat can result from batteries, HVAC service power, a condensate float, loose seating or loss of low voltage. Do not jumper wires.
Open record HVAC · condensateWater is collecting around the furnace or air handler
Shut cooling or condensing heat off when water approaches wiring. The source may be a blocked drain, pump, frozen coil, humidifier or plumbing.
Open recordStructured 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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