Goodman GMNT 100 failed ignition - http://www.hvacmechanic.com/ Forums

Original message

SteveK46825

74.129.211.37

"Goodman GMNT 100 failed ignition" , posted Mon 20 Oct 21:01

Hi All - I stumbled across this site while trouble shooting my Goodman GMNT100-4 furnace and thought I would give it a try. This is a used furnace that I had installed in my workshop (professional install) - it has been in place for almost 2 years without any issue. It is also fueled by Propane.

When the thermostat trips, it turns on the furnace as normal . The blower motor kicks in (draft motor?). The ignitor begins to glow a short time after this,and then the gas valve supplies gas. This is where things start to go wrong. There are 5 "burners" / tubes. The first one with the ignitor begins to burn
the propane, but the other 4 tubes never begin to burn.

I pulled the front cover so I could watch the circuit board and after it cycles a few times, it shuts down and the indicator light blinks once indicating failed ignition (yeap, it failed to ignite properly). Listed problems include gas pressure and ignitor. The ignitor is new.

I did check the obvious and the propane tank (500 gallon) is 40 percent full. I did not check pressure post regulator as I have no easy way to do that currently.

Am I looking at a propane regulator problem or is it possible it is the gas valve itself? Any other thoughts?

This problem started gradually and now it will not ignite fully at all.

Ideas?"

Replies:

techshawn

70.52.160.10

"Re(1):Goodman GMNT 100 failed ignition" , posted Mon 20 Oct 22:44:

1.check burner orifices. Confirm no clogged.
2.check the flame spreader for clog.The spread is located above burners,acrossing burners,like a bridge, spreading flame one another. You mentioned that only one burner is firing, that's because the spreader didn't spread and ignitor the rest of burners.
3. and because only one burner is firing, flame rod didn't sense flame for other burners, so shut off itself.

see this pic.

http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BURN1822507&Category_Code=burners

I like fixing everything.

[this message was edited by techshawn on Mon 20 Oct 22:47]

SteveK46825

74.129.211.37

"Re(2):Goodman GMNT 100 failed ignition" , posted Mon 20 Oct 23:03

Thanks tech shawn - So based upon your response, I should remove the burner assembly and clean? Correct?

Is this normal? I have owned a few furnaces and never heard of a burner plugging up - especially with a furnace of this age - it has a date of manufacture of 2001/2002.

Thanks..

SK

SteveK

techshawn

70.52.160.10

"Re(3):Goodman GMNT 100 failed ignition" , posted Mon 20 Oct 23:21

well, I was trying to be logical. look, this is your mention,
"The first one with the ignitor begins to burn
the propane, but the other 4 tubes never begin to burn."

From the above comment, I thought the flame was not spread from the first burner through the others. I think this is the first step you need to take. You said it's a used one, there could be buildup inside the spreader or elsewhere.

I like fixing everything.