Furnace Troubleshooting: 10 Issues and How to Fix Them

By: Diana Rodriguez-Zaba
Updated on: March 13, 2019

When your furnace suddenly stops working, the temperature in your home seems to drop by the minute. You’re on the phone trying to line up help, but you know HVAC technicians stay extra busy this time of year. The whole situation leaves you cold and frustrated.

Is it enough to make you think about trying a little DIY furnace troubleshooting?

Before putting your name on the waiting list for furnace repairs, take a look at our 10-point guide. When we help customers with our furnace cleaning services, we often point out fixable problems that don’t have to turn into expensive wintertime headaches.

10 Signs the Furnace Isn’t Working: What You Can Do

furnace issues

Get a jump on these 10 common furnace issues by digging out your owner’s manual. If you can’t find it, take a look at the label on your unit. Note the model, serial number and manufacturer’s date, and use that information to locate an online version of your furnace manual.

1. Inconsistent Airflow

Furnace airflow problems can result in cold rooms, hot spots and even damp basement walls. Make sure all vents are open to maximize air circulation, and replace dirty filters. Don’t forget the large furnace filter positioned between the main register duct and the blower chamber.

2. Water Around the Furnace

If you see water puddling around the furnace, check the condensate line and drain. Clear out clogs, or replace the tubing. Follow up with chemical tablets in the condensate pan to discourage slime build-up and mold growth.

3. No Pilot Light

Before you troubleshoot the pilot light, turn off electricity and gas connections to the furnace. Try tightening the thermocouple rod connected to the gas valve. You can also adjust flame size with the component’s turn screw. Reference your manual for details.

4. Malfunctioning Thermostat

Remove the thermostat cover, and gently clean recessed areas with a hand vac or soft brush. Pull out the old batteries so that you can take care of corrosion with an electronic contact cleaner. Put in fresh batteries, and make sure you’re not having furnace issues with the breaker or fuse that powers the thermostat.

5. Broken Fan

Test this component by turning off the heat at the thermostat and then setting it to fan only. If you don’t hear the fan engage, check for a tripped circuit breaker. If the fan still doesn’t come on, it probably needs replacing. This is a big DIY job, so you might consider calling in your HVAC pro.

6. Worn-Out Capacitor

When the furnace isn’t working, it can be something as small as this fan motor part. The capacitor ensures timed electrical charges that keep the unit running smoothly. Turn off the furnace’s electricity, disconnect the capacitor’s wiring, and test it with a multimeter. If readings register below its marked rating, replace the part.

7. Faulty Blower

The blower in your furnace works with the fan, but this equipment can develop its own problems. Make sure the door on its housing is securely closed. Otherwise, it won’t operate properly. Check the blower belt for signs of wear. If it looks frayed, reference your furnace manual for specs on a belt replacement.

8. Overloaded Motor

The blower motor can become overheated especially if the furnace hasn’t been cleaned recently. Dust build-up and an oily film create enough friction to interfere with proper operation. Let a hot blower motor cool off for half an hour, press its reset button, and make arrangements to have the furnace cleaned as soon as possible.

9. Closed Gas Valve

You can head off many furnace issues with DIY maintenance, but some glitches are simple oversights. If your inspections and testing don’t reveal anything obvious, locate the furnace gas line. Follow it from the side of the unit to the shut-off valve. Make sure the valve hasn’t been accidentally closed.

10. Bad Smells From Vents

Remove vent covers, and use a flashlight to look inside the ductwork. If you see dirt, debris and mold, imagine what it’s like further in. Eliminate the problem with the same air duct cleaning services that commercial properties use to maintain fresh, healthy indoor air quality.

Be Prepared for the Cold

furnace cleaning

We know your DIY talents can cover just about anything around the house, and we’re here to back you with a full line of furnace cleaning services. Be sure to share our troubleshooting guide with friends and family. Our Comments Section is always open to your input, and we look forward to your feedback.

We’re all hoping for an easy winter, but we want you to be prepared when the coldest weather blows through. Contact our teams here at ServiceMaster Restoration by Zaba for the best duct and furnace cleaning services in Chicago and the suburbs. You’ll sleep warmer and safer too. Just give us a call.