Top 10 Furnace Problems

Top 10 Furnace Problems

A broken furnace is one of the most frustrating things that can happen to a homeowner. As a result, we everyone has to solve problems related to our heating systems at some point. To total all of the furnace-related issues, it might seriously go up a hundred. But here are the top 10 most encountered furnace problems by our technicians.

1. Dirty Flame Sensor

This is seriously the reigning champion – this sensor problem is always in the first place. When it comes across a dirty flame sensor, the complaint is usually, seems the furnace is working and they can hear it turn on. They can even hear the burners coming on, but they only stay on for a few seconds and they shut right off.

Those signs almost guaranteed they’re experiencing a dirty flame sensor. The flame sensor gets dirty with time and once there’s enough build-up on it, your furnace will stop sensing the flame.

Don’t worry, all you need to do is clean the flame sensor.

It is a stainless-steel rod which will be behind the burners. It could be on the top or at the bottom of the burners. It is usually on the opposite side of the igniter.

Please remember when taking it out, make sure you turn off your furnace power switch. Not all flame sensors are easy to access, but many of them are pretty accessible.

Clean it with a Scotch Brite pad and don’t use sandpaper on it. Just grab your flame sensor and press the Scotch Brite pad hard on it and rub it until it shines up.

2. Dirty Furnace Filter

The filter is generally going to be on your return duct right before the furnace. The filters are directional. Most of them will have an arrow on them that says which way the air flows, is the way you should put the filter in. Whatever side has a net on it, that’s the side which goes towards the blower fan or the furnace.

The reason for the dirty filter is if for some reason, somebody doesn’t replace their filter for a long time, it’ll get restricted and the fan will start to suck it in.

There are times when the filter gets completely sucked in and wrapped around the motor shaft. It’s really hard to pry it off. That’s why one side of the filter has a net on it to prevent it from being sucked in.

Ideally, you should be changing the filter every month or two and the best filters to buy are the fibreglass filters which are either blue or green.

There are premium filters where the accordion is just closely knit together. They tend to be a little too restrictive. So, the one highly recommended is the medium-grade pleated filter, where the accordion is a little more spaced out. These tend to catch the most stuff and they’re, not as restrictive.

When your furnace seems to not be keeping up or the burners come on for a couple of minutes and turn off, or maybe when it’s colder outside your furnace, isn’t keeping up. Generally, it will be because your furnace is overheating.

Every furnace has a high limit switch, if the furnace inside is getting too hot because there’s not enough air going through it, then the high limit trips – and it turns the burners off. It leaves the fan on to cool itself Off and then turns back on.

It repeats this cycle over and over and some furnaces have a lockout feature. If it overheats three to five times in one heating cycle, it’ll go into a lockout for three hours or it’ll just sit there and do nothing.

3. Bad Inducer Motor

Problems on the inducer motor could show signs such as it’ll be scorching hot or there are times when it’s not hot.

In those cases, you want to check with your meter and see if it’s getting 120 volts from the control board. Because sometimes it’s the board has a problem and not the inducer motor where it’s just not sending power to it.

If the inducer motor is getting 120 volts, but it’s not turning on, the inducer motor is the problem. The only other scenario is if your motor has something stuck in it like some bird’s nest.

An easy way to check it is sometimes you’ll have a cooling fan in front of your inducer motor. There’s a fan behind the grates. You can try to stick anything which fits in there and spin it. See if it is spinning freely. If it is, we could say it means you probably don’t have anything stuck in there and your inducer motor is just bad.

Of course, the easy fix for it is to just replace the whole inducer motor. Usually, they come as a little assembly, which makes them pretty easy to replace.

4. Bad Blower Motor

The blower motor is usually on the bottom section of the furnace. It has a housing and every blower motor will have a capacitor.

If you reach in on the other side generally, you can put your hand in there and spin the blower wheel or the squirrel cage by hand. Now, if the blower motor is bad or seizing up, you won’t be able to freely spin the fan.

Another indicator is, if you reach in there and touch the motor, it’ll be really hot. The reasons why the blower motor fails are because the filter is dirty for a long time, the electrical surge, or the capacitor is dead.

The little capacitor gives the fan a boost to get it spinning. If the capacitor is completely dead, the fan will have a really hard time turning on. If the fan starts very sluggishly and then completely quits, or there is a burnt electrical smell in the house, then almost guaranteed the blower motor is bad.

Of course, the remedy is to replace the blower motor. If the wheel is bad, replace the wheel and you always replace the capacitor as well.

5. Bad Control Board

The control board looks differently on various furnaces. Older furnaces will not have control boards, just have a few relays. But most furnaces will have aboard.

The control board could be the culprit if the furnace is not working at all. Early signs could be when the sequence of operation is suddenly interrupted and the light codes indicate electrical issues.

The common reasons for the control board to fail are faulty wiring and a dirty control board.

6. Bad Gas Valve

The gas valve is right in the upper section of the furnace, just above the burners. Sometimes it’ll be below, but, if your gas valve is getting power, yet it’s not opening, then it just means the solenoid on the gas valve is bad.

And generally, you can’t just replace the coil on it. You have to replace the whole gas valve.

What happens in the furnace, in this case, is the furnace will start up normally, where the inducer motor will start the pressure switches, then will close, igniter glowing and then nothing else happens.

It just glows and then shuts off. You can hear the gas valve opening. It’ll produce a click sound but no gas comes out.

In that case, the furnace is simply just not getting gas. So, if it is the problem, then you just need to replace the whole gas valve.

7. Bad Igniter

Your igniter is on the right side of the furnace. Usually, it will have a Molex plug you can unplug.

When the furnace turns on, it seems to start working, but it never actually lights. Turn the furnace switch off, turn it back on and see what it does. You’ll see the inducer motor come on after a while.

Generally, you will hear the gas valve opens and a little bit of gas will come out, but the igniter was never glowing most of the time. It means your igniter is bad and if you want to check it with the meter, you can put your leads into the plugin the metal parts.

If the igniter is getting 120 volts, but it’s not glowing, then you know you have a bad igniter or you can turn the power off to your furnace. Unplug your igniter and then set your meter to resistance and put both leads into both plugs. Once you replace it, your furnace should fire right back up.

8. Bad Ignition Module

A bad ignition module is a control board, but the difference between a control board and an ignition module or ignition control is the ignition module is only for the ignition.

It only controls the gas valve, the spark and the flame sensor, whereas the control board controls both the gas part and the fan, which is why sometimes it’s called the IFC which stands for Integrated Furnace Control.

What it’ll be doing is if it’s a spark igniter, for some reason, it won’t be sending the spark to the igniter, or maybe it’s not sending power to the gas valve. To check it, you would have to test it with your Meter.

You would just check if it’s sending power to the gas valve or if it’s sending power to the spark. If it’s not, then the Ignition Module is bad and needs to be replaced.

9. Bad Thermostat

Sometimes when you turn on your furnace or even your fan and nothing happens, it could be just one of the thermostats or the furnace is not working. Take the thermostat off the wall and jump R to W, which is jumpering the heat call.

When the furnace turns on and everything works well, in that case, it’s just the thermostat is bad and nothing’s wrong with the furnace.

10. Dirty Pilot Assembly

It is an intermittent pilot system. It’ll have a little pilot hood, a spark igniter generally and a flame sensor.

What happens is it’ll have a silver tube coming out of the gas valve, which is the pilot tube. The pilot tube opens up, first releases gas into the pilot to light the pilot intermittently or when there is a call for heat.

The little pilot lights and once the flame sensor proves there is a little flame there, then it will tell the gas valve to open up and light all the burners.

What happens is the little pilot tube which goes to the pilot hood, there’s a little orifice in there. If there’s some gunk, that falls on it, maybe some scaling or some rust, dust or any kind of debris, the little pilot orifice will get plugged up and the pilot flame will not be hitting the flame sensor.

All you got to do is take the whole thing out. Sometimes you can get away with just taking it out from the bottom and then being careful on how you bend the tube so you don’t kink it. Just get it out far enough where you can take apart that pilot assembly to get to the orifice.

You have to take off the knot and just take the whole thing out to get to the orifice and clean it out. Use just a brass brush, clean it up, and then you put everything back together and everything works.

We hope you found this article useful. Thank you so much for reading to the end. Does any one of these issues sound familiar to you? A heating system repair professional can then be scheduled to come to take a look.

A furnace tune-up can help you avoid costly furnace repairs in the future.