Hey, I'm Shane with a handle on things If you've got a Goodman brand
furnace like the one I've got, or any other gas operated furnace and the furnace won't turn on or the furnace won't ignite a basic understanding of how gas furnaces operate might save you a lot of trouble,
and maybe a lot of money so stick around I'll show you the four main things that usually fail and keep a gas operated
furnace from working properly and I'll show you how I fix them on my furnace So here's my situation, I live a gazillion miles from nowhere and I have a Goodman gas furnace that
provides the primary heat for my house and every year or two when summer comes to a close I turn on the furnace and something doesn't want to work right with it.
Well guess what… summer just came to a close I turned on my furnace and it doesn't want to light. Well let's see if we can sort this out and
get a handle on things in the furnace room! My furnace is located in a small furnace room so getting to it can be a bit tricky especially for filming Here's a quick tip! Put your furnace model number and serial number in a spot where they're very
easy to find when you need them This will save you a lot of aggravation later Let's pull the access panels
off the furnace and have a look I'll remove the top panel
where the burner is located And the bottom panel where the
control board can usually be found In the bottom compartment
there's a safety door switch If the plunger on this switch is out of
position because the access door is off the furnace won't run The control board has line voltage supplied to it in my case that's 115 volts I'll be careful what I touch in here ! In the upper compartment
we find the pressure switch It's attached to the blower fan with a rubber hose This is the burner assembly On the flame side of the
burners we find the igniter Hey could you do us a favor? Take just a second and hit
that like and subscribe button! You wouldn't believe how
much it helps the channel out thanks! …and the flame sensor On the side of my furnace is
an electrical shutoff switch…
And the gas supply shutoff valve all of the switches and sensors on the
furnace connect to the control board my furnace isn't lighting so I'm going
to have a look at the igniter first the igniter is connected by a
plug in the upper compartment After shutting down the breaker to the furnace
and shutting off the gas supply for safety I'll detach the igniter at the plug The igniter is held in place
with two sheet metal screws After removing the screws
the igniter lifts out easily This igniter has a lot of soot built up on it and I found a crack in the porcelain So I'm going to replace it I ordered a new igniter from eBay it cost me about 15 bucks the furnace part shop in town wanted
60 bucks for the same igniter! I inspect the new igniter there should be no breaks in the coil everything looks good The holes in this mounting plate
are the same distance apart as the other igniter so it's looking good so far I install the new igniter and plug it back in The plug is set up so it
only goes together one way can't mess this one up While I'm at it I'll clean the flame sensor it's also located in front of
the burners on this furnace I remove the one screw holding
it in place and pull it out The flame sensor also has soot on it it doesn't have to be very dirty
and the furnace will start acting up so I'll clean it The flame sensor is cleaned with acetone Fingernail polish remover that's the same thing I never use abrasives to clean this sensor There's only one wire attached
to the sensor and it looks okay I reinstalled the sensor the pressure vacuum switch tells the control
board that the burner blower fan is working It knows that because the fan
creates a suction through the rubber tube that trips the pressure switch I detach the rubber hose and verify
that the hose is in good condition Then I suck on the rubber hose
and listen to the switch click This is an indication that the suction
will cause the switch to operate This doesn't mean the switch is good, but it does mean it's tripping
with pressure at least I've had plugged hoses But I've never had a bad switch…
Well… yet I plug the hose back into the fan housing after replacing the igniter, cleaning the flame sensor, and checking the pressure switch, I check to see if the furnace is now working Usually it'll work fine at this point and
i can close up the furnace and move on. I've turned the thermostat up, turned the gas on, and turned on the power.
And I'm holding the door switch
in to check the furnace operation The burner fan has come on
and it's evacuating any gas that may be present prior to the ignition sequence Well at this point the
igniter should start glowing but that isn't happening that's not a good sign after about two minutes the furnace
starts blinking a failure code this is a single flash code it keeps repeating but it's a single flash code I check the chart to see what
a single flash code means and I have an ignition failure I've already checked the things it says to check a quick look at the furnace
schematic tells me that the igniter should be getting 115 to 120 volts
of ac power when it's supposed to initiate the schematic says that bold lines
are high voltage and thin lines are low voltage on this furnace Now this is a multimeter You can get one at a home improvement
center for as little as 10 bucks You really ought to have one I set it to read up to 200 volts of ac power And I plug the leads into the wires that are
supposed to supply the line voltage to the igniter It doesn't matter which lead
goes to which wire with ac power Then I cycle the furnace again to see how much power the control board is supplying
when it's time to ignite the furnace Well the control board isn't sending any
power when it's time to ignite the furnace.
I now know that something is
wrong with the control board After all, the igniter can't
work if it isn't getting power so I shut off the breaker and
the gas supply again for safety the control board is mounted to the furnace
on a series of little plastic buttons A little squeeze on the plastic buttons
and they release the control board easily The control board part number is printed
in the margins of the control board I'm going to need this so that
I can order a new control board Well…
Now I guess we know why the
control board quit me don't we This mouse shorted the high voltage
side of the control board with his body He won't be doing that again anytime soon! I found a new control board on
eBay for less than 100 bucks The furnace parts store in town? Yeah… they wanted 200 bucks for the same board Try not to give the new board a static shock? Well, tell that to the mouse ! I checked the part number on the new board… people make mistakes sometimes. this looks like the right one though Then I checked the paperwork
that came with the new board to make sure they haven't made any improvements
that are going to require my attention no surprises on this one that's good now we're going to remove the wires
from the old board one at a time and plug them into the correct
locations on the new board one at a time is the key that way you can't get confused the nine pin connector can only
plug in one way that's a no-brainer okay I one-at-a-timed my way through
all of the wires and connections and the new board is now all hooked up I'll pop it back onto the
little plastic mounting buttons Time to turn on the breaker
and the gas supply again And then I'll hold the door switch in and we'll see if the furnace will light this time if all things are working the igniter
should start to glow after about a minute and there it is and…
the furnace lit and it kept running! now that's a good deal! now just for those of us who want
to see how many volts the igniter should be getting if the board is working right There it is… 123 volts ac that's line voltage in this case I zip tied all the wires again… and I'm going to clean up this
filthy furnace just a little bit And with the access panels back on my furnace
now works exactly like it's supposed to Well, I'd say that I saved myself
about 600 bucks on this project ! but the truth is that most of the furnace guys
I've run into don't like replacing control boards they would have just tried to
sell me a new furnace instead So i saved a ton of money!.
