The Easy Guide to Diagnosing a Bad Furnace
Inducer Motor Hey guys, today I wanted to expand on our
recent gas furnace troubleshooting series. “The Easy Guide to Diagnosing a Bad Furnace
Inducer Motor” will fill you in on what the inducer motor does, why it’s important,
the most common of ways I’ve found inducer motors fail, and how to let the customer know
what you’ve found. That’s coming up here on Fox Family Heating
& Air. If this is your first time watching our channel,
please click subscribe down here on the bottom right. And if you click that little bell next to
it, you’ll be notified of all our videos as they come out. First, I want to give fair warning to anyone
watching this that is not already an experienced technician in the HVAC industry. This video is for educational purposes only. Fox Family Heating and Air does not recommend
anyone other than a professional to start opening the furnace up and trying to diagnose
the failure going on with your system.
There are high and low voltages that can shock
a person. There are also lots of moving parts that can
damage body parts. Namely hands and fingers. The furnace also produces hot surfaces within
the furnace compartments and around the housing which can cause severe burns. There is an actual flame that is produced
by the ignition and startup of a gas furnace which can cause severe burns and damage to
person or property. First, as a technician, you have to know the
sequence of events that occurs for a gas furnace to start up properly. It’s really easy, and you should have this
memorized before you can even consider being qualified to troubleshoot. 1. Power to the furnace control board
2. Thermostat signals the call for heat
3.
Inducer motor kicks on
4. Pressure switch proves the inducer operates
correctly 5. Ignitor activates
6. Gas valve energizes
7. Flame pours across burners
8. Flame sensor proves all burners are lit
9. Blower forces air through the ducts
When a furnace begins a new cycle, the inducer motor is the first thing you should see kick
on. 120 volts is applied through the wires coming
from the control board. This starts the inducer motor for up to 60
seconds before anything else even happens. It’s a safety feature that creates a negative
pressure or draft which purges the heat exchanger of any poisonous gasses, namely the biproducts
of combustion. It makes the air inside the heat hollow tubes
of the heat exchanger cleaner when the flame kicks on. When we have cleaner air inside the heat exchanger
at the time of combustion the efficiency of the furnace increases. Without going into it too much, there’s
a safety device called a pressure switch that activates when the diaphragm inside of it
recognizes the suction or purging action of the inducer motor. There’s another video called The Easy Guide
to Diagnosing a Bad Pressure Switch, and I’ll make sure it’s attached to the end screen
so you can check that out.
But first, you’re wanting to know more about
the inducer more and how to troubleshoot it. If the inducer motor doesn’t turn on when
it’s supposed to, the furnace will recognize this and shut down. It will wait a bit and try again. If the motor doesn’t start after 3 to 5
tries, the control board will stop sending voltage to the inducer motor, and essentially
locking it out from attempting it anymore. So, let’s go into why inducer motors fail. If the correct voltage is applied to the motor
and it’s not turning on, something’s not right.
Let’s dig into why:
Unplug the furnace, which removes power to the system. Is the base of the motor warm or hot to the
touch? This means the that it’s been trying to
spin, but something is holding it up. Is the flywheel on the motor, or the actual
squirrel cage unable to spin when you manually try to turn it? This can be a solid indicator that the motor
is bad and needs to be replaced.
Why is this happening? One reason the shaft of the motor to lock
up is the bearings on the motor could be seized preventing it from turning. Another reason has to do with the windings
inside the motor. One of them could be open. Usually the start winding in this case. And finally, some motors have a capacitor
that starts the motor and regulates the voltage while its running. If it is a bad capacitor, a new one should
get it going again. One of the first indicators that an inducer
motor is on borrowed time is if it starts making odd noises. Sometimes it’s a rattling noise, a clanking
noise, chattering, pinging, shaking, a wobbling noise – You name it! If it comes on, and is running any other way
than what you interpret as normal based on your training and experience with properly
operating furnaces, you can take a look at it and see if it’s something you can physically
adjust.
If not, the inducer motor should be considered
bad. Why? Because it’s not running to manufacturers
specs. Think about it like this. Would the builder of the furnace, who takes
a ton of pride in the operation of their system, send this out into the field to be installed
knowing the inducer motor is making a god-awful noise? The answer is a resounding no! And you have to know that and be comfortable
telling the customer this. Because many inducer motors are nearly impossible
to rebuild, an entirely new unit must be purchased in most cases when one wears out. One of the exceptions to this is the occasional
Carrier or Bryant units. So at this point, this is what I need my technicians
to do. Inducer motors are ordered through the manufacturer.
And since we have flat rate pricing which
includes the cost of parts, labor and warranty, if the motor is less than $100, it is a level
7. Above $100 is a level 8. $200 and above, they need to call supervisor
for pricing. You want to know the pricing and availability
before you talk to the customer, because you want to minimize the number of times you need
to bring the customer information. Coming to them and telling them the inducer
motor is bad just to hear them say, “Okay how much is it?” making you go find out,
just to come back, to tell them it’s such-and-such price. You get the approval on the price, but they
want to know when the repair will take place.
This makes you have to call back to parts
warehouse to ask when the part will be available. Then you have to go back to tell them the
part will be in around 5 to 7 business days from the factory. All of this back and forth can be avoided
if you have the information for them up front, before you even tell them about the diagnosis. Even if they don’t go with your repair,
you have the information and can log it in your file for the customer in case they call
back, approving the repair a month from now. Once we determine pricing and availability,
it’s time to talk to the customer about our diagnosis. We explain what we found, let the customer
know the price, and let them know when we can come back to repair the system. And, Just a word to the wise, good communication
between you and the customer would be telling them you need to change this part on the furnace
before you can see if anything else is wrong with the system. Sometimes you’ll get a customer that asks,
“So this will fix my system, and get it going again, right?” Well, you don’t really know, because you
haven’t seen what the rest of the start-up sequence and the cycling off of the system
is doing, have you? It’s very likely the rest of the system
will work since multiple failures are pretty rare, but you’re gonna feel like a jerk
if you forget to tell them you have to see how the rest of the system operates after
you replace the inducer motor.
Coming back to them after you’ve replaced
the motor and saying, “Oh yeah, now your gas valve isn’t working, that’ll be another
$600.” So just remember, without a properly functioning
inducer motor, there’s no way to tell if the rest of the system is working to manufacturer
specs. If it is a part that’s available for pickup,
call the office to determine a date to pick it up and return to replace. If it is a part that needs to be shipped,
we want to let the customer know that the part should be arriving at said date and that
we’ll call to schedule the appointment when the part arrives. Another thing you’d want to communicate
to the customer and the office is how long the repair will take. During installation of the inducer motor,
we need to make sure to either replace the gasket, (usually comes with the new motor),
or make a gasket with high temp silicone.
Once installed, a good technician will test
the system for proper operation to make sure there are no other issues with the furnace. So, just to recap, inducer motors pull the
flame through the heat exchanger and vent the exhaust through the roof. In order to determine failure of an inducer
motor, we need to verify the proper voltage is being sent to it. If the motor has proper voltage, the capacitor
tests good, and is not turning on, the motor is bad. If it’s making a lot of noise, the homeowner
should know the part is working but is on borrowed time. If this is your first time watching our channel,
please click subscribe down here on the bottom right. And if you click that little bell next to
it, you’ll be notified of all our videos as they come out. Thanks so much for watching and we’ll see
you on the next video..
