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Furnace Repair2019-11-22T21:12:00-05:00

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Furnace Repair Guide – Costs, Common Issues & DIY Troubleshooting Tips

Proper furnace repair and maintenance are mandatory if you want to get the most extended life, best performance, and highest efficiency from your heating system.

Here at, we know that having a furnace isn’t the same thing as knowing about furnace maintenance, and there are plenty of homeowners out there who want to learn more about furnace repairs and upkeep for their heating systems.

For that reason, we’ve created this comprehensive guide that will tell you everything you need to know about furnace maintenance services. Which includes common problems and questions, troubleshooting help, and even average repair costs.

Please note, the following is for informational purposes only. Any servicing you attempt is at your own risk.

Individual Furnace Brand Repair Guides

Amana Furnace Repair Guide
American Standard Repair Guide
Armstrong Furnace Repair Guide
Bryant Furnace Repair Guide
Carrier Furnace Repair Guide
Coleman Furnace Repair Guide
ComfortMaker Furnace Repair Guide
Continental Furnace Repair Guide
Daikin Furnace Repair Guide
Goodman Furnace Repair Guide
Heil Furnace Repair Guide
KeepRite Furnace Repair Guide
Lennox Furnace Repair Guide
Luxaire Furnace Repair Guide
Napoleon Furnace Repair Guide
Rheem Furnace Repair Guide
Ruud Furnace Repair Guide
Tempstar Furnace Repair Guide
Trane Furnace Repair Guide
York Furnace Repair Guide

Common Furnace Problems

1. Dirty filter

Dirty filters will result in a lower efficiency rating, reduced performance and heating capabilities, lower air quality, and a furnace that doesn’t last as long as it should. Furnace filters should be changed every one to three months.

2. Lack of maintenance

Your furnace has a lot of working parts, and for the unit to perform optimally and efficiently, these components have to be serviced regularly. A good rule of thumb is to have your heating system inspected and tuned up once a year by a certified HVAC technician.

3. The unit doesn’t heat/work

Plenty of things can cause this problem, from something as simple as the unit not getting power because a breaker tripped or fuse blew to something complicated like a faulty heat exchanger. Other possible causes include a defective thermostat or wrong thermostat setting, and problems with the gas line, ignitor, or pilot.

4. Improperly sized unit

When investing in a new heating system, a crucial consideration is the size of the unit and its heating output versus the size of the space you’re heating. If the furnace is too small, it will run constantly, cost a fortune to operate, and won’t keep your home warm enough. But a furnace that’s too large is also a problem because it will frequently cycle, allow your home to cool between cycles and increase humidity levels.

5. Improper installation

You spent a great deal of money on your furnace, so you’re going to want to make sure it’s installed properly, working well, and not going to need repairs in a few months because of installation errors. The only way to ensure the furnace is installed right is by hiring a trained and certified local contractor. This is especially important with gas furnaces because the last thing you want is a gas leak from a botched installation job.

6. Thermostat problems

Thermostats do break down, and when this happens, they aren’t able to properly control heating cycles. If you think your thermostat might be malfunctioning, replace it with a new one and make sure it’s adequately calibrated and set according to your comfort needs.

7. Dirty flame sensor

The flame sensor is a safety feature that prevents the furnace from exhausting gas when there’s no flame present. If this small metal rod gets dirty, it won’t be able to detect the flame and will shut the furnace down, resulting in a system that comes on when it should but then shuts down before it can heat the house.

8. Pilot problems

Older furnaces have a pilot light that stays burning all the time, and if it goes out because of a draft, clog problem with the thermocouple, or other reason, then the furnace won’t be able to do its job.

9. Fan motor

The fan motor powers the blades that circulate air around your house, and if the motor is faulty or breaks down, then the fan won’t operate at the right speed and won’t keep your home at the right temperature.

How to Perform Furnace Repairs

Frequently Asked Questions

The good news about furnace maintenance is there are many simple things you can do that will extend the life of your heating system and keep it working optimally. For one, change the filter every one to three months (see below). You should also vacuum the blower and fan blades regularly to keep them free of dust, and inspect the vents from time to time to check for dirt and debris, and clean them as needed.

You can also check the chimney annually for cracks and damage, and inspect the fan belts to make sure they’re intact. You should also hire a certified technician once a year for inspection and servicing.

Turn off the furnace. Locate the filter, which is usually on the right side of the unit. Slide out the old filter and, using the arrows for guidance, slide the new filter into place. Turn the unit back on.
There are lots of issues that can cause your furnace to make funny sounds, and you may even be able to diagnose the problem based on the noise. For instance, a furnace that rattles, squeaks, or rumbles probably has a mechanical problem, such as a faulty belt or loose panel. Grinding noises often indicate a problem with the motor.
The simplest and most common causes of this include a dirty air filter, improper thermostat setting, or a poorly sized unit. If the furnace isn’t heating at all, it could be a power/fuel supply issue, broken blower motor, malfunctioning heat exchanger, or problem with the pilot light or ignitor.
First, check that the unit is getting power and that the breaker didn’t trip or a fuse didn’t blow. Next, check your thermostat to make sure it’s set to Heat and at a comfortable temperature. See that the access panel is attached correctly, otherwise, the safety switch might be engaged and preventing the furnace from operating. If you have a pilot light, make sure it’s burning.
Open the access panel and locate the flame sensor, a small metal rod near the pilot. Scrub it carefully with a non-abrasive pad to clean off dust, residue, and dirt.
Change the thermostat setting to Auto to prevent the fan from running when the furnace isn’t in a heating cycle.
This is usually because of the thermostat’s heat anticipator. Check the settings to make sure they’re correct, clean the inside of the thermostat, and replace the device if you think the thermostat is faulty.

Signs that your furnace is on its last legs include:

  • Corrosion on the unit
  • The unit isn’t producing Heat or isn’t producing enough Heat
  • Regular pilot light failures
  • Delayed ignition after a call for Heat has been made

The average lifespan of a furnace is 13 to 20 years, with most lasting around 15. When your furnace is older than 10 years and no longer under warranty, you should consider upgrading to a new unit if your old unit requires significant repairs, especially to expensive components like the heat exchanger.

Furnace Repair Pricing and Parts

One thing you have to do as a homeowner is budget for furnace repairs and maintenance, so it helps to know what those repairs might roughly cost.

To help you budget for the various repairs, we’ve put together a general guide to furnace repair prices when you hire a contractor, followed by a description of the services (from least to most expensive):

Annual inspection, thermostat repair, flame sensor or ignitor repair: $80 to $300
Limit switch replacement, burner repair, or gas valve replacement: $115 to $470
Replacing the thermostat, blower fan, or circuit board: $125 to $650
Replacing the furnace motor or heat exchanger: $1,200 to $2,400

$80 to $300

When you schedule an annual inspection and maintenance, the HVAC contractor will:

  1. Check the air filter and replace it if necessary
  2. Clean the outdoor unit, including the fan blades, blower, and coil
  3. Check the thermostat and settings and calibrate it if necessary
  4. Inspect the unit for signs of wear and tear, cracks, damage, and other issues
  5. Ensure the furnace switch is working
  6. Lubricate moving parts
  7. Check the condensate drain and access vents for blockages
  8. Test airflow, the pilot or ignitor, gas or oil lines, and fuel pressure
The thermostat is the device that monitors the temperature in your home and communicates with the furnace to initiate and stop heating cycles. When there’s a problem with the thermostat, it might not initiate heating cycles, might cycle too frequently, and will cause erratic temperatures in your home.
As well as becoming dirty, the flame sensor can also fail, and this will similarly cause the furnace to cycle on and off too quickly. A related problem involves the hot surface ignition, which is used in modern furnaces instead of a pilot to ignite the burners.

$115 to $470

This is a safety device that’s responsible for shutting the furnace off should the system overheat. When a limit switch fails, it needs to be replaced. Otherwise, the furnace will cycle erratically.

The burner is where fuel is burned to provide Heat for your home. If the burner malfunctions, it will need to be repaired or replaced for the furnace to work.
The gas valve controls the flow of gas (fuel) in your heating system. A dirty gas valve that’s clogged with dirt or residue will need to be cleaned, and a gas valve that stops opening will need replacement.

$125 to $650

Sometimes thermostats malfunction or break down to the point where they can’t be repaired, and in those cases, they have to be replaced.

Once the burner heats the air, the fan blows it into the ductwork to be distributed around your house. When this component malfunctions, the fan isn’t able to circulate air properly.
The circuit board connects all the electrical components in the furnace, and it will need to be replaced if it becomes damaged or corroded, or otherwise malfunctions.

$1,200 to $2,400

The furnace motor is what powers the fan that circulates air throughout your house, and it can malfunction or break, preventing the fan from working properly.

The heat exchanger is what heats the air that gets circulated around your house, so it’s one of the most important components in your furnace and also one of the most expensive to repair or replace if it gets damaged, cracks, or breaks down.

Basic Furnace Repair Tools

Screwdriver to open the access panel
New filter when replacing the old one
Non-abrasive pad to clean the flame sensor
Vacuum to clean the blower and fan blades
New thermostat if the old one is faulty

Furnace Repair Safety Tips

Never perform any repairs or maintenance on your furnace without first shutting off power to the unit

Test your carbon monoxide detectors monthly if you have a gas or oil furnace

Make sure the area around your furnace, including the air intake, is free of debris, furniture, clutter, and especially flammable items like wood, papers, and some chemicals

Always read the owner’s manual before performing any maintenance, and follow all safety and repair instructions carefully

If you smell gas, shut the unit off, open the windows, and get everybody out of the house immediately before calling your utility company or the fire department

Use parts and replacement components that are made for your specific furnace

If you suspect the heat exchanger is cracked, contact an emergency HVAC contractor immediately, because it could lead to a gas leak (look for visible cracks, corrosion, and a clicking sound from the furnace when the blower shuts off)

HVAC Help and Maintenance

Knowing how to diagnose and troubleshoot some of your furnace repairs can be very rewarding, but there are times when you’ll need help from a trained professional.

During these times, you want a technician you can rely on, and that’s why we created our independent contractor certification program. With this program, you can find a trustworthy and dependable HVAC technician in your area who has all the right licences and certifications, training, experience, and more.

Need help with air conditioner repair and troubleshooting? Check out our A/C Repair Guide section.

Furnace repair certified partners

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All the proper licenses & certifications
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