Troubleshooting reference
Start with symptoms, rule out homeowner-safe basics, and escalate conservatively when safety, structure, utility service, or water damage is involved.
Emergency
Carbon monoxide alarm sounds or furnace flame is yellow/sooty
Likely causes
- Cracked heat exchanger
- Blocked flue or vent
- Improper combustion or gas pressure
Homeowner-safe check
Leave the home, call 911 or the gas utility, and do not restart the appliance.
When to call
Hire an HVAC pro only after emergency responders clear the building; require combustion readings in writing.
Call soon
AC or heat pump runs but does not cool
Likely causes
- Dirty condenser coil
- Low refrigerant from leak
- Failed capacitor, contactor, or compressor
Homeowner-safe check
Replace the filter and clear debris around the outdoor unit; do not add refrigerant yourself.
When to call
Call soon if temperature split is poor, ice appears, or the breaker trips.
Call soon
Furnace will not start or starts then locks out
Likely causes
- Dirty flame sensor
- Failed igniter
- Pressure switch or venting fault
Homeowner-safe check
Check thermostat mode, breaker, filter, and furnace switch; do not bypass safety switches.
When to call
Call if lockout repeats, you smell gas, or the venting path is suspect.
Call soon
Ice forms on refrigerant lines or indoor coil
Likely causes
- Restricted airflow
- Low refrigerant charge
- Blower motor or metering device failure
Homeowner-safe check
Turn cooling off and fan on to thaw; replace a dirty filter and keep panels closed.
When to call
Call before restarting if ice returns or airflow is weak.
Emergency
Breaker trips when outdoor unit starts
Likely causes
- Shorted compressor or fan motor
- Weak capacitor
- Damaged wiring or disconnect
Homeowner-safe check
Reset once only if there is no burning smell; repeated resets can worsen electrical damage.
When to call
Call immediately if the breaker trips again, hums, or feels hot.
Routine
Rooms are uneven: one side hot, one side cold
Likely causes
- Duct leakage or imbalance
- Closed dampers/registers
- Wrong equipment sizing
Homeowner-safe check
Open supply/return registers and replace filters; avoid closing many registers to force air elsewhere.
When to call
Call routinely for duct balancing, static-pressure testing, or load calculation.
Call soon
Thermostat is blank or system ignores settings
Likely causes
- Dead batteries or no common wire
- Tripped float switch
- Failed thermostat or control board
Homeowner-safe check
Replace batteries and check the condensate safety switch if the pan is dry and accessible.
When to call
Call if condensate is wet, wiring is loose, or the thermostat repeatedly loses power.
Call soon
Condensate water leaks around indoor unit
Likely causes
- Clogged drain line
- Cracked drain pan
- Improper trap or slope
Homeowner-safe check
Turn cooling off if water is spreading and clear only an accessible cleanout with a wet/dry vacuum.
When to call
Call soon if ceiling/wall damage starts or the float switch keeps tripping.
Call soon
Heat pump blows cool air in winter
Likely causes
- Normal defrost cycle
- Aux heat not energizing
- Low refrigerant or reversing valve problem
Homeowner-safe check
Verify thermostat is on heat, not emergency heat, and wait through a short defrost cycle.
When to call
Call if supply air stays cool, outdoor unit ices solid, or energy use spikes.
Call soon
System short-cycles every few minutes in heating or cooling mode
Likely causes
- Oversized equipment satisfying the thermostat too quickly
- Dirty flame sensor or pressure switch interruption on furnace calls
- Low refrigerant, frozen coil, or high-pressure cutout on cooling calls
Homeowner-safe check
Replace a dirty filter and record cycle length; do not bypass safeties or add refrigerant.
When to call
Call an HVAC technician when short cycling continues after a clean filter or happens with lockout codes, ice, or burner shutdown.
Maintenance schedule
Seasonal tasks
Spring
- At the first cooling run, replace the filter, rinse cottonwood from the outdoor coil gently, and confirm the condensate safety switch area is dry.
Summer
- During heat waves, keep two feet clear around the condenser and write down supply-air temperature complaints by room, not just thermostat readings.
Fall
- Before heating season, test carbon-monoxide alarms, install a clean furnace filter, and verify return grilles are not blocked by furniture.
Winter
- After snow or ice, clear heat-pump stands, furnace intake/exhaust pipes, and dryer-like sidewall vents without chipping at plastic fittings.
Interval tasks
Monthly
- Monthly, inspect filters, listen for inducer or blower changes, and check that the condensate pan or floor around the air handler stays dry.
Annual
- Yearly, schedule combustion analysis or cooling service before peak weather, especially for furnaces, boilers, older AC units, and heat pumps.
Every few years
- Every few years, reassess duct leakage, thermostat strategy, refrigerant history, and equipment age before replacing parts piecemeal.
Cost components
Labor
Airflow testing, refrigerant diagnosis, combustion readings, duct access, controls, and equipment set-up time decide crew hours; the base scope includes diagnostic depth, combustion/refrigerant testing, duct access, equipment weight, startup commissioning, and whether electrical or gas corrections are bundled.
Materials
Material risk sits in capacitors, motors, boards, coils, line sets, plenums, filters, thermostats, pads, and safety switches; ordinary allowances cover filters, capacitors, motors, boards, refrigerant components, line sets, thermostats, duct fittings, furnaces, condensers, coils, and heat pumps.
Permits and inspections
Inspection cost belongs in the quote when equipment changeouts, fuel-gas work, electrical disconnects, condensate routing, and duct alterations trigger review. Ask who files and who meets the inspector.
Broad range discipline
Tune-up visits, component repairs, and full system replacement with duct or electrical work set the practical budget ladder. Service calls and tune-ups are low-ticket; motors, boards, and refrigerant leaks are mid-ticket; full furnace/AC/heat-pump systems are major projects with wide brand and efficiency spreads.
What moves price
Pushes price up
- Emergency heat/no-cool calls; added cost is usually tied to airflow testing
- Hard attic/crawlspace access; added cost is usually tied to refrigerant diagnosis
- Duct replacement or static-pressure fixes; added cost is usually tied to combustion readings
- High-efficiency variable-speed equipment; added cost is usually tied to duct access
Can reduce price
- Routine shoulder-season scheduling; lower pricing is likelier when capacitors is clearly defined
- Clean filter and clear equipment access; lower pricing is likelier when motors is clearly defined
- Like-for-like replacement with reusable ductwork; lower pricing is likelier when boards is clearly defined
- Maintenance-plan discounts; lower pricing is likelier when coils is clearly defined
Hiring red flags
- A quote that shrugs off combustion testing after burner or heat-exchanger work is not a trade-ready scope.
- Verification of airflow and static pressure before adding refrigerant is missing from the bidder's process.
- The low number removes Manual J or duct review on replacement equipment along with useful proof photos.
- Callback terms never address compressor, heat-exchanger, coil, and labor exclusions in practical detail.
- No Manual J or AHRI match for replacement equipment.
- Adds refrigerant without leak discussion or EPA-certified handling.
- Ignores carbon monoxide, venting, or combustion documentation.
- Prices a system over the phone without seeing ductwork, panel, or equipment.
Contract checklist
- Equipment model numbers, AHRI match, thermostat, filter size, and accessory scope with brands, sizes, locations, and exclusions.
- Load calculation basis, duct modifications, refrigerant line reuse, and condensate route before work starts, including who schedules inspections.
- Combustion-air, venting, clearances, CO testing, and startup readings for access, protection, cleanup, and disposal.
- Unit prices for pad, disconnect, plenums, zoning dampers, drain safety devices, and crane access as unit pricing or written allowances.
- Commissioning sheet, warranty registration, permit inspection, rebate documents, and old-equipment disposal; final paperwork should include photos, manuals, registration proof, and waivers.
- Equipment model numbers, AHRI match, efficiency ratings, and thermostat included.
- Load calculation, duct/static-pressure assumptions, and airflow targets.
- Permit, inspection, refrigerant recovery, and startup commissioning checklist.
- Electrical/gas/venting corrections and who performs each licensed scope.
- Manufacturer registration, labor warranty, and maintenance requirements.
Warranty norms
HVAC workmanship is commonly one year, but compressors, heat exchangers, coils, and control boards follow brand terms that may require registration. Refrigerant leaks, dirty filters, blocked coils, improper thermostat settings, and unapproved add-ons are common exclusion fights.