Simple Furnace Fixes

If you suspect furnace problems, try these 8 quick furnace fixes you can do yourself before calling a pro.

Next Project
Time

A full day

Complexity

Beginner

Cost

Less than $20

Introduction

If your furnace quits or breaks down try these eight simple solutions before you call for service help. You can solve the furnace problems and avoid a $200 service call.

Tools Required

  • 4-in-1 screwdriver

Materials Required

  • Bleach
  • Electrical tape
  • Furnace filter
  • Hardware cloth
  • Metal foil duct tape

Watch this video to see 6 quick DIY fixes for furnace problems:

Project step-by-step (8)

Step 1

Check the thermostat to make sure it’s on

Thermostat controls

family handyman

Move the thermostat setting to “heat.” A furnace can be intimidating—especially when the heat won’t turn on. However, there is good news from furnace maintenance pros. Roughly a quarter of all service calls could be avoided with easy furnace fixes that cost little or nothing. In this article, we’ll focus on the common furnace troubleshooting culprits and show you what to do about furnace problems.

Thermostat not turning on heat

Before you assume you have a furnace problem, do some furnace troubleshooting and check the thermostat to make sure it’s actually telling the furnace to come on. Thermostats, especially programmable ones, can be complicated, and the more options a thermostat has, the more that can go wrong.

  • Make sure the furnace switch is on “Heat” rather than on “Cool.”
  • Check the temperature setting.
  • Compare the temperature setting to the room temperature. Set the temperature five degrees higher than the room temperature and see if the furnace kicks on.
  • Make sure the program is displaying the right day and time, as well as a.m. and p.m. settings.
  • Trace the thermostat wires back to the furnace to check for breaks, especially if you’ve done any remodeling recently. If you find a break in one of the thin wires, splice the line back together and wrap it with electrical tape.
  • Replace the battery. If you have a power outage with a dead battery, you’ll lose your settings and the thermostat will revert to the default program.
  • Open the thermostat and gently blow out any dust or debris. Make sure it’s level and firmly attached on the wall, and that none of the wires coming into it are loose.
  • If you can’t make the program settings work, you can bypass them altogether. Simply punch in the temperature you want with the up/down control and then press the hold button. That will switch on the furnace if the thermostat programming is the problem.

Tip: Lost your owner’s manual? Most major-brand manuals are on the Web—just go to the manufacturer’s website.

Figure A Furnace Troubleshooting: 8 Things to Check Before You Call a Repair Service

family handyman

You can check and correct all eight items in just a few minutes. We show a gas-fired, forced-air furnace here, but most of the same checks apply to electric furnace systems and hot water boilers.

Note: You can download Figure A and enlarge it in Additional Information below.

Step 2

Check shutoff switches and breakers

APR17_Reset_Breaker_1-2

It sounds unbelievable, but furnace technicians often find that the only “repair” a furnace needs is to be turned on. Look for a standard wall switch on or near the furnace—all furnaces, no matter what age or type, have one somewhere. Check the circuit breaker or fuse for the furnace as well. Make sure the front panel covering the blower motor is securely fastened—there’s a push-in switch under it that must be fully depressed for the furnace to operate.