how to repair a furnace

by Lenny Brakus Published 3 years ago Updated 2 years ago

Simple Furnace Fixes

Check the thermostat to make sure it's on. Move the thermostat setting to “heat.” A furnace can be intimidating—especially when the heat won't turn on.
Check shutoff switches and breakers. ...
Change filters. ...
Make sure the gas is on. ...
Make sure the chimney exhaust flue is clear. ...
Flush out drain lines. ...

Full Answer

How to know if your furnace needs repair?

How to Know if Your Furnace Needs Emergency Repair

Heating System Is Outdated. Furnaces have a lifespan of about 15-20 years on average. ...
Blows Cold Air. When the heater is on, but you feel cold air being pushed out of the system, it’s time to get your unit checked by a professional.
Creates Strange Noise. ...
Has a Faulty Pilot Light. ...
Increased Heating Bills. ...
Reach Out to Home Comfort Experts! ...

What is the best way to repair a furnace?

What We Found

If you’re getting low airflow, check the air filter on the furnace; a clogged filter could cut airflow to a trickle.
See whether there are loose wires or a malfunction in the thermostat. For an electronic thermostat that runs on batteries, try changing them.
Are fuses burned out or circuit breakers tripped? ...

How to know when to repair vs. replace your furnace?

The cost of the repair vs. the cost of a replacement
The age of your system
Your budget and comfort goals

How do you troubleshoot a furnace?

Other Ways for Troubleshooting your Furnace

Check the furnace flame
Pilot light and gas valve
Properly secure front panel
Ensure all vents are open and unblocked

Can you fix a furnace yourself?

With a little do-it-yourself experience, you can troubleshoot and repair your furnace yourself. Your best bet though, is to have a maintenance check list for your heating system to avoid the problem.

How do you fix a furnace that won't heat?

0:123:07How to fix a furnace that won't heat EASY FIXES - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe first thing you can do is the easiest thing and that is to check the air filter if your airMoreThe first thing you can do is the easiest thing and that is to check the air filter if your air filter is dirty your furnace will kick on maybe run for about three minutes or so and then shut off.

What can cause a furnace to stop working?

Common Reasons Your Furnace Isn't WorkingThermostat Not Set to On. ... Circuit Breaker Flipped. ... Clogged Air Filter. ... Access Panel to Furnace Not On Properly. ... Dirt or Other Things Blocking Furnace Air Flow. ... Burners Are Not Clean. ... Furnace Not Lubricated Properly. ... Bad Limit Switch.More items...

How do I get my furnace to work again?

How to Reboot a FurnaceChange the Filter. Before you do anything, check the furnace filter. ... Check the Pilot Light. If the pilot light is off, your furnace can't get the spark necessary to light the boilers. ... Turn the Furnace Off and Back On Again. ... Call a Certified HVAC Professional.

Why is my furnace running but not blowing heat?

When you turn the furnace on but no heat comes out, there may be an obstruction. Dirty air filters restrict airflow, which can make it feel like not much heated air is coming out of your vents. Check the furnace filter and replace it if its surface is covered with contaminants.

Why is my furnace running but no heat?

Dirty filters are the most common cause of furnace problems. Dust and dirt restrict airflow—and if the filter gets too clogged, the heat exchanger will overheat and shut off too quickly, and your house won't warm up. If the blower is running but no heat is coming out, replace the filter.

How do you diagnose a furnace problem?

Furnace Troubleshooting Recap:Clean or replace air filter.Troubleshoot thermostat problems — replace batteries if necessary.Set thermostat to heat and at a higher temperature than the current room temperature.Check electrical panel for blown fuses or tripped breakers.Make power switch near furnace is flipped on.More items...•

How do I know if my furnace fuse is blown?

0:317:38How To Replace a Fuse on a Furnace or AC Air Handler Control BoardYouTubeStart of suggested clipEnd of suggested clipNothing will happen at all if that fuse is blown it. Means absolutely none of these controls downMoreNothing will happen at all if that fuse is blown it. Means absolutely none of these controls down here are going to work because all the low-voltage controls. That come from the thermostat.

How do you manually reset a furnace?

How to Reset an Electric FurnaceFirst, turn off the power supply to the furnace by turning off the breaker in the circuit box.Locate the reset button on the furnace and press it to reset the furnace. ... If the button is popped up, press it down.Return the cover to the blower compartment and turn the power on.

Why my furnace is blowing cold air?

If your furnace is blowing cold air in your home, this is a sign of an issue with the flame detector, gas supply, air filter, pilot light, or condensate lines. Many of these issues are able to be easily solved on your own by sanitizing or replacing components in the gas furnace.

Can hear your furnace click on but it does not fire up?

Most likely, your furnace is making a clicking noise and not providing heat because your furnace's spark igniter is trying to ignite your pilot light or burners but is failing to do so. In other words, there's an ignition system malfunction that needs to be fixed. Otherwise, your furnace won't start.

Why is my furnace not responding to thermostat?

When a furnace is not responding to a thermostat, there is either a problem with the heating unit or the actual thermostat. Lack of power to the thermostat, wrong settings, and outdated software might be to blame, as well as faulty wiring, a tripped breaker, and a dirty furnace filter.

What do you do when your furnace is blowing cold air?

How To Troubleshoot Furnace Blowing Cold AirStep 1: Check Thermostat Setting. First and most importantly, make sure your thermostat is set to Heating Mode. ... Step 2: Evaluate and Adjust Your Vents: ... Step 3: Assess Furnace Filters and Replace Filters If They Are Dirty. ... Step 4: Call An HVAC Pro.

How do you reset a furnace?

How do I know if my ignitor is bad on my furnace?

Here are a few indications that you have a faulty ignitor.No Cold Air. ... The Furnace Won't Come On. ... The Furnace Suddenly Stops Blowing. ... Starts, Then Stops, Then Starts Again. ... Tripping the Breaker More Than Once. ... I Hear the Click, But Nothing Happens. ... Flame Sensor Problems. ... Short Circuit.More items...•

Why won't my furnace stay lit?

If it won't stay lit after several attempts, you may have faulty thermocouple. If pilot flame still won't stay lit, call professional service person. Some furnaces have an electrical system to ignite the gas; in these systems there is no pilot light. Instead, an electric element heats up and ignites the burners.

What are the problems with natural gas furnaces?

Most natural gas furnaces have few operational difficulties. Problems typically. involve the pilot light, the thermocouple, or some part of the electrical system. On some gas furnaces and heaters, a plug-type door covers the pilot light assembly. To gain access to the pilot burner, pull the door out of the furnace housing.

How high should the pilot flame be on a gas stove?

To adjust the height of the pilot flame, turn the flame adjustment screw until the flame is from 11/2 to 2 inches high.

How far apart should you set the pointer for gas leaks?

The pointers should be set about 25 degrees apart. Set the upper pointer at about 115 degrees Fahrenheit and the lower one at about 90 degrees Fahrenheit. If you smell gas while performing these repairs, you'll want to get that leak taken care of right away. Learn how to find gas leaks on the next page.

How to replace a thermocouple?

Step 1: Unscrew copper lead and connection nut inside threaded connection to gas line. Under mounting bracket at thermocouple tube, unscrew bracket nut that holds tube in place. Step 2: Insert new thermocouple into hole in bracket.

How to access pilot burner on a furnace?

To gain access to the pilot burner, pull the door out of the furnace housing. On other units, remove the panel that covers the pilot and gas burners. The pilot light controls, reset buttons, gas valves, and thermocouple are usually contained in an assembly at the front of the furnace.

Why does my pilot light go out on my furnace?

The pilot light on a gas furnace can go out because of drafts. To relight the pilot, follow the manufacturer's instructions exactly; they are usually fastened to the furnace. If instructions for relighting the pilot are not provided, follow this general procedure: Step 1: Find pilot light assembly.

What causes furnace problems?

We talked to the experts at Superior Heating, Air Conditioning & Electric in Anoka, Minn., to get the lowdown on which furnace problems generate the most service calls, which of those repairs can be performed by a DIYer and which ones are “pro only.” It turns out that most of the problems are caused by a clogged furnace filter or any of three easy-to-fix parts—the igniter, the flame sensor and the furnace high-limit switch.

Why won't my furnace restart?

Replace it with a new one. Then reset the furnace (Photo 2). If the furnace won’t restart, the repeated overheating may have damaged the high-limit switch. Consult the wiring diagram on the furnace door or your service manual to find its location. Then test it (Photo 3). If the switch is bad, remove the retaining screws and pull it out of the heat exchanger, noting the position of the sensor. Install the new switch with the sensor facing as it was.

Why does my furnace igniter crack?

However, over time, the constant heat/cool cycles cause the igniter to crack and fail.

How much does a furnace flame sensor cost?

So it makes sense to keep spares on hand. Igniters and flame sensors cost about $50 each at appliance parts stores and furnace dealers. Or you can find them for less online. But first you’ll need the make, model number and serial number of your furnace. Find all that information on the manufacturer’s label (Photo 1).

Why does my furnace overheat?

A clogged air filter restricts airflow through the heat exchanger, causing the furnace to overheat. The high-limit switch detects the dangerous overheating and signals the computer to shut off the burners and run the blower fan to cool off the heat exchanger. Once the furnace cools, the computer tries to fire up again.

How does a condensing furnace work?

Condensing gas furnaces attain their efficiency by extracting water from the exhaust gases. Sometimes condensation from that exhaust can form in the pressure switch tubing. This silicone tubing runs between the flue and the heat exchanger and the safety furnace pressure switch. Experts tell us they usually remove those tubes and blow them out with compressed air as a preventive measure (Photo 6).

How to hold an igniter in place?

The igniter can be held in place either by screws or by a snap-clip arrangement. Use a lighted flexible mirror to discover the method used on your furnace. Then remove the screws or unsnap the retainer and remove the old igniter. Use care when you install the new igniter—it’s brittle and can crack or shatter easily (Photo 4).

What to do if your furnace is clogging up?

If you have a furnace that vents out the side of the house, make sure nothing is blocking the intake or exhaust. If either of the pipes is covered with screen mesh (like window screen), replace it with 1/2-in.-mesh hardware cloth. If ice is clogging one of the pipes, you have a bigger problem somewhere in the system. Clear it off and call a technician to find out why it's happening.

How long does it take to check a furnace?

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.

Why does my furnace shut off?

Dust and dirt restrict airflow—and if the filter gets too clogged, the heat exchanger will overheat and shut off too quickly, and your house won't warm up.

How much water does a furnace drain?

High-efficiency furnaces can drain off several gallons of water a day in heating season. If the drain lines become restricted by sediment or mold growth, the furnace will shut down. If the drain hose looks dirty, remove the hose, fill it with a mixture of bleach and water (25 percent bleach), then flush it after several minutes.

How to clean a thermostat that is not loose?

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.

How to check for a break in thermostat wire?

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.

Why is my gas furnace not blowing hot air?

Gas furnace not blowing hot air? Just as with switches, someone may have turned off a gas valve and then forgotten to turn it back on. Trace the gas line back from the furnace to the meter, and if you see a handle that's perpendicular to the gas pipe, turn it so it's parallel. Gas furnace repair is depends on how old your furnace is. If you have an old furnace or boiler, you may have a pilot light. Remove the front panel and the burner cover and check to make sure it's lit.

Why does my RV furnace shut down?

Should the flame that is burning the gas in the combustion chamber go out, it will most certainly shut down your RV furnace to avoid gas from continuing to flow into the furnace. Providing the gas is being burned properly, it is possible the flame sensor is bad. The flame sensor is most likely part of the ignitor assembly.

How to test a furnace sail switch?

Action: Clean the blower fins and sail switch and retest. If they are clean and the furnace doesn’t come on, you can test the sail switch with a multimeter.

What does a flashing light on a furnace mean?

The circuit board on your furnace will most likely have a light that indicates errors. Certain flashing patterns will indicate the problems to start looking for. This, combined with the actions or the inactions of the furnace, will put you on the right track.

What does a thermostat do?

The thermostat sends an electrical signal to the furnace circuit board.

What does the signal on a furnace mean?

The signal continues to the high-level switch which indicates the temperature of the furnace is below a safe level to start.

Why does a high level switch shut down a furnace?

There are a couple of possible reasons for this: a leak in any of the tubes in the combustion chamber can create excess heat or improper exhausting of hot air.

What happens if a fan doesn't run on battery power?

If the fan doesn’t run on the battery power, then the fan is the problem and your relay is likely fine. 2. The fan comes on but the furnace doesn’t fire. Situation: You hear the fan start but the furnace doesn’t fire.