How to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating SystemHow to Service Your Furnace and Heating System

How to Service Your Furnace and Heating System — Iowa

Complete checklist with climate-adjusted recommendations for Iowa

Overview

Have a technician inspect the heat exchanger, clean burners, check gas connections, and test safety controls.

Hire a ProAdvanced~90 min

Step-by-Step Guide

Schedule a professional tune-up before heating season

Book an HVAC technician for a fall tune-up before you need the furnace. September or early October is ideal — wait until November and you may face a weeks-long wait.

Replace the air filter (homeowner task)

This is the one part you should do yourself. Locate the filter slot (usually between the return air duct and the blower compartment). Slide out the old filter, note the size printed on the frame, and insert a new one with the airflow arrow pointing toward the furnace.

Technician inspects the heat exchanger

The technician will visually inspect the heat exchanger for cracks or corrosion. A cracked heat exchanger can leak carbon monoxide into your home and typically requires furnace replacement.

Technician cleans the burners and flame sensor

The burners are removed and cleaned to ensure even flame distribution. The flame sensor rod is cleaned with fine sandpaper or emery cloth — a dirty flame sensor is the most common cause of furnace short-cycling.

Technician checks gas connections and pressure

All gas connections are inspected for leaks using a combustible gas detector or soapy water. Gas pressure is measured at the manifold to confirm it matches the manufacturer's specification.

Technician tests safety controls

The high-limit switch, pressure switches, and ignition system are tested. These controls shut down the furnace if dangerous conditions are detected. The technician verifies each one triggers correctly.

Technician inspects the flue and venting

The exhaust flue is checked for proper draft, blockages, and corrosion. For high-efficiency furnaces with PVC venting, connections are inspected for separation or damage.

Test the thermostat and full heating cycle

The technician runs the furnace through a complete heating cycle, measuring temperature rise across the heat exchanger and checking that the blower fan operates at the correct speed. The thermostat calibration is verified.

What You'll Need

Tools

- New air filter (correct size for your furnace)
- Carbon monoxide detector (verify yours is working)

Materials

- Replacement air filter (the only part homeowners should handle)
- Fresh batteries for your CO detector

Cost Estimates

DIY Cost

$5 - $30 for a replacement air filter (the only DIY portion)

Professional Cost

$80 - $200 for a professional furnace tune-up; $300 - $600 if repairs are needed

Safety Tips

Never attempt to clean burners, adjust gas pressure, or inspect the heat exchanger yourself. These are tasks for a licensed HVAC technician.
Install carbon monoxide detectors on every level of your home and near sleeping areas. Test them when the furnace is serviced.
If you smell gas (rotten egg odor) at any time, leave the house immediately and call your gas utility from outside.
Do not close more than 20% of your supply registers — restricting airflow can cause the heat exchanger to overheat and crack.

When to Call a Professional

This entire task requires a professional. Furnace service should be performed annually by a licensed HVAC technician.

Pro Tip

Ask the technician to show you where your filter is located and how to change it. Change it every 1-3 months during heating season. A clean filter is the single most important thing you can do to keep your furnace running efficiently.

Common Mistakes to Avoid

Skipping annual service because the furnace 'seems fine' — heat exchanger cracks and gas leaks are invisible until they cause problems.
Putting the air filter in backwards — look for the airflow arrow on the filter frame and point it toward the furnace.
Closing too many supply registers to 'redirect heat' — this increases static pressure and can damage the blower motor or crack the heat exchanger.
Using the cheapest fiberglass filter available — a MERV 8 to MERV 11 pleated filter captures far more particulates without restricting airflow.

Related How-To Guides

How to Inspect Attic Ventilation and Insulation

Check that soffit vents are clear and ridge or attic fan is working. Proper ventilation prevents heat buildup.

How to Check Your Chimney and Fireplace

Have the chimney inspected and swept if you burn wood. Check damper operation and firebox condition.

How to Reverse Ceiling Fan Direction for Winter

Set fans to clockwise (looking up) on low speed to push warm air down from the ceiling.

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