Furnace Checklist

If you're running into problems with your furnace, be sure to check the following items to eliminate a service call.

Check your thermostat batteries!

The first thing to check is always your thermostat. Most thermostats are powered by batteries. Some thermostats are wired to get power from your furnace and do not require batteries, especially wifi thermostats. If you have a nest thermostat pop the thermostat off the wall and check that you have a wire going into the "C" terminal on the base plate. If you do not, you will want to get a new wire ran or use a wire saver to get the thermostat all the wires it needs to operate properly.

How is the air filter doing?

All furnaces have some sort of filter on the return side (usually sticking out on the side of the furnace). You should never-ever operate a furnace without a filter for more than a few hours. Turn the furnace off at the switch usually mounted on the side of the furnace and slide the filter out to check. A dirty air filter can cause your furnace to overheat and shut off on a safety temperature limit switch. If your furnace filter is indeed plugged please remove it and give the furnace 10-15 minutes to cool down, and get a new filter and slide it in and start it up. You'd be surprised how many filters cause furnaces and air conditioners to stop functioning. Please be sure to be a routine filter change schedule. 1" thick filters should be changed every 1-3 months at the least, thicker filters can get 6-12 months depending on use. We encourage twice a year AT LEAST to change your filter.

Is the switch on and is the breaker on?

There is a switch usually on the furnace that looks like a standard light / electrical switch you see around your home. Many times we see where kids or others are in the basement and they flip the switch thinking it's a light. Make sure it is in the on position.

Is the furnace telling you something?

Most modern high efficiency furnaces have circuit boards that communicate errors. You can sometimes look into a port hole on the door. The furnace board will flash usually off and on steady if everything is good. If there are problems it may turn red and flash a pattern out. Write that down and if you need us to come out to your home communicate that code when calling in. You should not have to open the furnace to get this flash, and if you have to, do not worry about it... we can handle it.

Are the drain lines clear, restricted, backed up?

Another common cause that can stop a furnace to stop functioning is the drain lines are plugged or backed up. High efficiency furnaces tend to have a blocked drain pressure switch that will stop the furnace if it cannot drain properly. Make sure the drain lines are clear. It's not uncommon for them to look pretty nasty with time but water can still usually flow ok. Try taking the hose off of the furnace and blowing through it. If you can it is good for now. Be sure there are no objects pressing on the drain.

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Questions & Answers

My furnace is working but sounds very loud.

Most of the time with modern furnaces and variable speed blowers is due to a restricted air flow. First step would be to turn off of the furnace at the switch, let the blower slow down and turn off. Check the air filter. Most of the time the loud blower is a sign of the plugged filter. If this is the case be sure to set a schedule to change these regularly as it can be damaging to your blower long term (and costly if the blower fails). If your filter is in good condition check around your house for any closed registers or restricted return registers (ones that do not have louvers). It also could be that the blower profile could be too high. If those two things do not fix it, it's best to call us out there. It could be the blower profile is set too high or something else is plugged up or needs diagnosing.

My furnace will only ignite for a few seconds and drops out.

This is a sign that you could have a dirty flame sensor or restricted venting. When the furnace goes through a start process it will purge and get fresh air in to use to burn. When it ignites it is checking to see that all flames ignited. There is a safety control in the last burner that needs to see a flame. Problem is, with it sitting in a flame so long it can start to coated in carbon build up. You can clean this with a very fine grit sandpaper or something as gentle as a $1 bill. Each furnace has a different process to remove the flame sensor. If you're looking for locations and help check youtube for a specific video to your equipment. If you have annual maintenance as recommended by manufacturers you would have this part cleaned yearly. Every contractor should thoroughly clean this as a part of their tune-up (or at least we can only hope... we do though!) If your furnace still won't start, check and make sure the PVC exhaust and intake pipes aren't restricted. Animals love to make a nest in them and kids love to throw things into the pipes. It doesn't take much for a venting to be thrown off triggering a pressure switch error on your furnace.

My furnace tries to start but I don't get any flame to ignite. It just keeps trying.

You can reference the answer above, it most likely has to do with a restriction in venting, bad ignitor or a dirty flame sensor. Check venting for restrictions, and be sure that the flame sensor is clean. You should not have to replace the flame sensor, unless you see non-stop problems and cleaning it cannot fix it. Very rarely do we ever have to replace them. It can also be that the ignitor has failed. If you see it glow then it may be fine. We check the ignitor as part of our tune-up service. Another reason annual tune-ups may be a good idea.

My furnace blower will not shut off.

Make sure your thermostat does not have the Fan set to On. This will cause your furnace blower to stay on 24/7. New variable speed furnaces have a slow circulate speed when the furnace or air conditioner is not calling. Older furnaces have a high speed circulate speed. If your furnace still has the fan running even with fan set to auto this could be an issue at your furnace with wiring or the circuit board itself.

My furnace has water all over the floor.

High efficiency furnaces produce water as part of the combustion because of how efficient it is. The drain can get cruddy over time and may need to be flushed out. Take the drain off of the side of your furnace and try blowing water through it. If that doesn't do it, it could be you have a collector box that is failed or another issue. We recommend having a technician out.