Heating and air conditioning repair: a plain guide

How heating and air conditioning repair works

A heating and cooling contractor diagnoses, repairs, maintains and replaces furnaces, heat pumps, air conditioners and the ducts and thermostats that tie them together. The contractor prices the visit, the parts and the labor.

What a contractor needs to know: what the system is doing or not doing, roughly how old it is, what fuel it runs on, and when you noticed the change.

What people call an HVAC contractor for

• Air conditioner repair: Warm air, short cycling, ice on the lines, a unit that will not start
• Furnace and boiler repair: No heat, uneven heat, a pilot or ignition problem, odd smells
• Heat pump service: Heating and cooling from one outdoor unit, including defrost problems
• Seasonal tune-ups: Filter, coil and safety checks before the heavy season
• System replacement: Sizing and swapping an old furnace, air conditioner or heat pump

Common jobs

Air conditioner not cooling

An air conditioner that runs without cooling usually points to airflow, refrigerant or an outdoor unit problem. A few details help the contractor bring the right parts.

A dirty filter or blocked return cuts airflow and can freeze the indoor coil. Ice on the lines is a sign to shut the system off and let it thaw.

Low refrigerant means a leak somewhere. Topping it up without finding the leak only buys time, so ask whether the contractor will look for it.

What to tell the provider

• Check the thermostat is set to cool and the filter is not clogged.
• Look at the outdoor unit: is the fan spinning, and is there ice on the copper lines?
• Note roughly how old the system is and when it last had service.

Furnace not heating

When the furnace stops heating, the cause is often ignition, airflow or a safety switch. Tell the contractor what you see and hear.

Modern furnaces shut themselves off when a sensor reads something wrong. A blinking light on the control board often tells the contractor which one.

An older furnace with a cracked heat exchanger can leak carbon monoxide. A working carbon monoxide alarm near the bedrooms matters more than any repair.

What to tell the provider

• Check the thermostat batteries and that it is set to heat.
• Check the furnace filter and that the furnace switch near the unit is on.
• If you smell gas, leave the house and call your gas utility from outside before anything else.

Replacing a furnace, air conditioner or heat pump

A replacement is a sizing question first. A contractor who measures the home gives you a better quote than one who matches the old unit.

A load calculation (often called Manual J) sizes the system to the house. An oversized system cycles on and off and can leave rooms humid.

Ask for the efficiency rating of each option and whether any utility or federal incentive applies before you sign.

What to tell the provider

• The age of the current system and any recent repair history.
• The rough size of the home and which rooms run hot or cold.
• Whether you want to compare a heat pump with a furnace and air conditioner.

Heating or cooling tune-up

A tune-up before the heavy season is a good time to catch a weak part. Ask what the visit covers.

A typical visit checks the filter, the coils, the electrical connections, the drain line and the safety controls.

Ask for a short written note of what was checked and anything that should be watched next season.

What to tell the provider

• Which system needs it: heating, cooling or both.
• When the filter was last changed, and its size printed on the frame.
• Any noise, smell or uneven room temperature you noticed last season.

What changes the price

• Diagnosis first: most contractors charge for the visit, then quote the repair.
• Parts vary a lot: a capacitor or igniter is a small part, a compressor or heat exchanger is a large one.
• For a replacement, the size of the home, the ductwork and the efficiency level drive the quote.
• Ask whether the quote includes permits, haul away of the old unit and any duct changes.

We never quote prices; the provider you hear from does.

Sources

• U.S. Department of Energy: Air conditioning
• U.S. Department of Energy: Furnaces and boilers
• U.S. Department of Energy: Heat pump systems