Goodman furnace (GMT 045-3B)

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  #1  
Old 01-03-21, 09:53 AM
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Goodman furnace (GMT 045-3B)

Model # GMT045-3B

Situation: When I turn the thermostat on, the motor cycles and turns off in less than 5 minutes. I hear the motor turn but I do not hear the ignitors or blower motor turn on.

The inducer motor turned on.
The ignitors did not turn on.

I removed the "flame sensor" cleaned it with scotch brite pad, reinstalled the flame sensor.
Turned the thermostat back on.
The inducer motor turned on.
The ignitors did not turn.

While waiting for the ignitors to turn on, I smelled gas.
I turned the system off.





Thanks
signal6271
 

Last edited by signal6271; 01-03-21 at 11:41 AM. Reason: more detail
  #2  
Old 01-03-21, 10:51 AM
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By blower, which do you mean? The inducer or indoor blower motor?
Here is the manual for those. How old is this furnace?

https://www.hvacpartsshop.com/conten.../gmph050-3.pdf
 
  #3  
Old 01-03-21, 10:53 AM
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Welcome to the forums.

Look thru the blower door at the flashing LED.
What is the blink code ?
Turn power off for one minute.
Turn back on and see what the furnace does and what flash code you get now.
You can post the code here or it will on the back of the blower door.

FYI.... opening the blower door will power the furnace down and clear the fault code.
 
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Old 01-03-21, 11:20 AM
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The red light is steady,
No blinking codes.
 
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Old 01-03-21, 11:27 AM
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Then the thermostat is not calling for heat.
Set it a little higher to get the furnace to start.
 
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Old 01-03-21, 11:31 AM
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Hello Pete,
Update.
The inducer motor turns on.
The ignitors do not turn on.
I have cleaned the flame sensor with a scotchbrite pad, reinstalled flame sensor.

I turned the thermostat on again and the-
The inducer motor turns on.
The ignitors do not turn on.

Thanks
Tony
 
  #7  
Old 01-03-21, 11:34 AM
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I just smelled gas,
and shut the system off.

 
  #8  
Old 01-03-21, 11:40 AM
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Yes... you will get approx 5-7 seconds of gas.

Ok..... your problem sound like a dead igniter. It is a hot surface igniter. You can unplug the wiring harness and check it for continuity. It should be 50 ohms or higher. If it checks ok.. you'd need to connect a voltmeter to the igniter leads to see if you get the 120v AC voltage.
Hot surface igniter

OEM part # B1401018S
Igniter at amazon
 
  #9  
Old 01-03-21, 11:42 AM
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The unit appears to be from 1999.
 
  #10  
Old 01-03-21, 11:47 AM
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When was the last time this furnace had any sort of preventative maintenance or cleaning?
 
  #11  
Old 01-03-21, 11:52 AM
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Looking at the ignitor parts, it appears to be two separate parts?
One is the flame sensor?
One is a flat igniter?
Is this correct?
 
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Old 01-03-21, 11:55 AM
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The filters get changed every 45 to 60 days.
I clean out the dust and debris from the side of the motor twice a year.
 
  #13  
Old 01-03-21, 12:11 PM
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What about cleaning the burners?
You could have a clogged burner jet.
Fuel burning equipment requires yearly service beyond filter changes. Especially when they age 10-15 years.
The flame sensor and igniter are 2 separate parts.
Ring out the igniter and see what your results are. You may have to disconnect the gas line and pull the burner assembly for cleaning.
 
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Old 01-03-21, 12:27 PM
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Taking the burner assembly is out of my training scope.
I will start with replacing the igniter and flame sensor first.
 
  #15  
Old 01-03-21, 12:32 PM
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Use your meter and measure the igniter first.
DO NOT blindly start replacing parts. The flame sensor is nothing more then a metal rod wrapped in porcelain. It’s an inanimate object. No reason to replace that at all.
 
  #16  
Old 01-03-21, 12:40 PM
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The igniter measured out at 10 to 12 ohms.
 
  #17  
Old 01-03-21, 12:45 PM
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Ok, your igniter may be the problem.
But if it’s been a long time since the burners were cleaned and the unit was inspected, I’d plan on that too.
Your unit is well into the time period where heat exchangers crack and rot. Which presents a carbon monoxide threat to those in the home.
Old doesn’t mean bad. But you need to make sure the unit is sound.
 
  #18  
Old 01-03-21, 12:56 PM
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Ok,
Another form member provided a part number for the igniter/flame sensor. OEM part # B1401018S
I will order the part and be back in touch.

I appreciate the comment on "don't blindly start replacing parts" it is what I typically do in the first place.

Thanks for the help.
Tony
 
  #19  
Old 01-03-21, 01:35 PM
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Always best to diagnose the issue first.
I tell my apprentices, the actual problem can not be a problem at all. Rather it is the result of the actual problem.
It teaches you about the equipment as well. And you can’t fix it if you don’t understand how it’s supposed to work.
 
  #20  
Old 01-03-21, 05:00 PM
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The igniter measured out at 10 to 12 ohms.
If you are sure of that..... it is good.
Most measure higher. Yours is showing continuity.

You will need to reconnect the igniter. Connect your leads to the same plug. Push the probes carefully in the connector next to the wires. You can turn the gas valve off. Call for heat. The inducer will run and in approx 20-30 seconds you should see 120vAC on the meter. If you don't..... that points to a bad control board.
 
  #21  
Old 01-04-21, 07:24 PM
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Update, remeasured the igniter at OL.
 
  #22  
Old 01-09-21, 08:54 AM
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Last update on this issue.
Issue repaired.
Thanks for the suggestions, the download link, and advice.

Take care.
 
  #23  
Old 01-09-21, 10:06 AM
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What was the end repair for the unit?
 
  #24  
Old 01-11-21, 11:23 AM
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End repair.
Flame ignitor replaced.
Unit back in operation.
 
 

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