Diagnose Home Repair Symptoms Room by Room

Symptom Guides · hvac

AC Short Cycling in an Older Home

Your older-home AC is short cycling most often because of restricted airflow (dirty filter or coil), an oversized unit for undersized ducts, low refrigerant, or a failing capacitor. Change the filter first, then have a licensed tech check static pressure and charge.

Symptom Guides · hvac

Furnace Bangs on Startup After Outage

A gas furnace bangs on startup after a power outage because of delayed ignition: gas pools in the burners before it lights, then ignites all at once. Shut it off and have the burners, igniter, and gas valve inspected.

Symptom Guides · hvac

Winter CO Alarm: Gas Furnace

A gas furnace usually triggers a CO alarm in winter from a cracked heat exchanger, a blocked or disconnected flue, or poor combustion air. Leave the house, call 911 or your gas utility, and don't relight the furnace until a licensed tech inspects it.

Symptom Guides · hvac

Furnace Pilot Won't Stay Lit in Summer

A gas furnace pilot that won't stay lit is almost always a failing thermocouple or a dirty pilot orifice. The thermocouple senses the pilot flame and keeps the gas valve open, so when it weakens, the valve closes and the pilot goes out.

Symptom Guides · hvac

Heat Pump Outdoor Unit Frozen Over

Light frost on a heat pump is normal in winter and clears during defrost cycles. Thick ice that never melts points to a failed defrost sensor, stuck reversing valve, low refrigerant, or a dead outdoor fan, all of which need a technician.

Symptom Guides · hvac

Heat Pump Struggling in a Cold Snap

A heat pump heats poorly in a cold snap when the outdoor coil ices over and the defrost cycle fails, or when the auxiliary backup heat doesn't engage to cover the lost capacity below roughly 35°F.

Symptom Guides · hvac

Heat Pump: High Bills Only Some Months

Intermittent high electric bills on a heat pump usually mean the backup electric heat strips are running when they don't need to, often triggered by cold snaps, a stuck defrost cycle, or low refrigerant charge.

Symptom Guides · hvac

Rooms Getting More Uneven in Temperature?

Worsening uneven room temperatures point to failing ductwork: leaking or disconnected joints, crushed flex sagging insulation, or unbalanced dampers.

Symptom Guides · hvac

Dust at registers after a renovation

Dust at your registers after a renovation happens because construction debris got pulled into the ductwork through unsealed returns while the HVAC ran. Cleaning requires a fresh filter, vacuuming accessible boots, and often a professional duct cleaning.

Symptom Guides · hvac

Older Home Ductwork Whistling Noise

Ductwork whistles when air is forced through a restriction, most often a dirty filter, an undersized return, or a gap in a duct seam. In older homes it's usually the return side struggling to feed a newer, more powerful blower.

Symptom Guides · hvac

HVAC Short Cycling After Power Outage

Your HVAC short cycles after a power outage because the interruption left the thermostat or control board in a fault or lockout state. A full power-down reset at the breaker usually clears it; if not, suspect a tripped safety switch or a surge-damaged control board.

Symptom Guides · hvac

Thermostat Drops WiFi in Winter

Your thermostat likely disconnects in winter because it lacks a dedicated C-wire and can't hold power during heavy heating cycles, or because it's on an exterior wall with weak WiFi signal.

Symptom Guides · hvac

Mini-Split Dripping Indoors in Summer

A mini-split drips water indoors in summer because its condensate drain line is clogged with algae and dust, causing the pan to overflow. Clearing the drain line usually stops it.

Symptom Guides · hvac

Mini-Split Flashing an Error Code

A mini-split shows an error code when its control board detects a fault (sensor, refrigerant, communication, or electrical) and shuts down to protect the compressor. Look up the exact code against your model number, because codes differ by brand.

Symptom Guides · hvac

Mini-Split Outdoor Unit Icing Up

Your mini-split outdoor unit is icing because its defrost cycle isn't clearing frost or refrigerant is low, causing the coil to run too cold. Light frost in freezing weather is normal, but thick ice that returns after thawing means a real fault.

Symptom Guides · hvac

Boiler: Intermittent No Hot Water or Heat

A boiler that intermittently loses hot water or heat is usually reacting to low system pressure, a dirty flame sensor, an airlock, or a failing pump or diverter valve. Check the pressure gauge first, then note whether it fails on heat, hot water, or both.

Symptom Guides · hvac

Boiler Pressure Keeps Dropping Faster

Your boiler pressure is dropping because water is escaping the sealed heating system, usually through a leaking radiator valve, a failed expansion vessel, or a weeping pressure relief valve. Faster drops mean a bigger or growing leak.

Symptom Guides · hvac

Older Boiler Relief Valve Leaking?

Your boiler relief valve leaks because system pressure is exceeding its rating (usually 30 psi), often from a failed expansion tank, or because the valve itself is worn and no longer seals. Check the pressure gauge first.

Symptom Guides · hvac

Humidifier Water Runs Constantly: Fix

A whole-house humidifier running water constantly usually has a stuck-open solenoid valve or a humidistat stuck calling for humidity. Shut the water supply to the humidifier, then replace the solenoid or reset the humidistat.

Symptom Guides · hvac

Static Shocks Won't Quit After Outage?

Static shocks persist after a power outage because your whole-house humidifier didn't resume normal operation, letting indoor humidity fall below 30 percent. Check the humidistat setting, water supply, and solenoid valve first.

Symptom Guides · hvac

Attic Fan Not Pulling Air in Summer

Your attic exhaust fan isn't pulling air because of a failed thermostat that won't trigger the fan, a stalled or slow motor from a bad capacitor, a broken belt on belt-drive units, or blocked soffit intake vents that starve the fan of makeup air.

Symptom Guides · hvac

Attic Fan Running, Humidity Still High?

Your attic humidity stays high because the exhaust fan can't pull fresh air in (blocked soffit vents), the humidistat is set too high or failed, or moisture is entering the attic from bathroom fans, roof leaks, or the crawlspace below.

Symptom Guides · hvac

Attic Fan Wiring Suddenly Overheating?

Attic exhaust fan wiring overheats when a connection loosens, the wire is undersized for the motor's draw, or a failing motor pulls excess current. Shut the circuit off at the breaker and inspect before running it again.

Symptom Guides · hvac

Radiant Floor: Sudden Cold Zones

Sudden cold zones on radiant floor heat are usually caused by trapped air in a heating loop, a stuck zone valve, or a failing circulator pump that stopped moving warm water through that section.

Symptom Guides · hvac

Radiant Pump Won't Circulate Steady

A radiant floor pump that runs intermittently is usually air-locked, cycling on thermal overload, or losing power from a loose connection or failing capacitor. Bleed the loops, check the wiring, and listen for a hum without spin before replacing the circulator.

Symptom Guides · hvac

Radiant Floor Heat Keeps Overshooting

Your radiant floor heat overshoots because the slab keeps releasing stored heat after the thermostat stops calling, and a stat without floor sensing or proper cycle tuning can't compensate. It worsens as sensor calibration drifts or settings shift.

Symptom Guides · hvac

Radiant Manifold Leak in an Older Home

Your radiant floor manifold is leaking because an aging O-ring, corroded fitting, or loose compression connection has failed. In homes over 15 years old, brittle rubber seals are the most common cause.