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Old 12-06-2011, 12:23 AM   #1
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Goodman Furnace Model Number GMNT080-4


I have Goodman Furnace Model Number GMNT080-4 that quit lighting. I have made checks on it and found that the igniter lights. It cycles on three (3) times and them shuts down. The igniters lights but there is no natural gas flow and it does not fire. In March 2011 I had a similar problem and found that I needed to replace the Gas Valve. After replacing it, I turned the gas on, and set the thermostat so that the furnace would start. The igniter started and then I heard the valve open and then gas flowed to the burners and then the furnace started. I have not had any problems since.

Today I replaced the gas valve again, and found that it does not activate gas flow to the burners. The igniter glows and is working properly. I checked and found that I have 24 volts at the valve. I also found that on the board, there is a red light that flashes 3 times.

Any help with this problem will be appreciated.

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Old 12-06-2011, 06:12 AM   #2
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Goodman Furnace Model Number GMNT080-4


your gas valve power is inline with the roll-out switches.... your furnace is KNOWN for heat exchanger failure! Call a PRO to have it examined!!!!!

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Old 12-06-2011, 07:43 AM   #3
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If that roll out switch was open the igniter would not glow. MSGbob what is the manifold pressure set at? what is the in-line pressure? these must be measured with a manometer before we can properly diagnose your problem.
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Old 12-06-2011, 08:46 AM   #4
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Goodman Furnace Model Number GMNT080-4


I don't have a meter to measure the gas pressure. Will have to call a tech to have it done. Thanks for your post.
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Old 12-06-2011, 08:48 AM   #5
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Goodman Furnace Model Number GMNT080-4


Don't have a meter to measure the gas pressure. Will have to call a tech in. Thanks for your help.
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Old 12-06-2011, 08:51 AM   #6
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Goodman Furnace Model Number GMNT080-4


I will call a tech in to have it looked at. I appreciate your assistance. Thanks much. I am just wondering how does a cracked heat exchanger cause the problems that I mentioned in my post?
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Old 12-06-2011, 02:58 PM   #7
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Goodman Furnace Model Number GMNT080-4


how did U check for 24 volts at the valve. across the 2 wires or from 1 to grd. if across then that is ok and the valve should open. if to grd that is wrong as the rollout is in series with the valve. you can have 24 to the valve and the other line is broken going to the rollout switch and opens the circuit so the valve won't open. if the heat ex is cracked then you get flame rollout.
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Old 12-06-2011, 03:40 PM   #8
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Goodman Furnace Model Number GMNT080-4


Quote:
Originally Posted by yuri View Post
how did U check for 24 volts at the valve. across the 2 wires or from 1 to grd. if across then that is ok and the valve should open. if to grd that is wrong as the roll out is in series with the valve. you can have 24 to the valve and the other line is broken going to the roll out switch and opens the circuit so the valve won't open. if the heat ex is cracked then you get flame roll out.
Yuri, again for the second time in one thread.........if the limit or roll out was open, then the igniter would not energize......he clearly states that igniter is glowing.
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Old 12-06-2011, 04:08 PM   #9
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Goodman Furnace Model Number GMNT080-4


Quote:
Originally Posted by harleyrider View Post
Yuri, again for the second time in one thread.........if the limit or roll out was open, then the igniter would not energize......he clearly states that igniter is glowing.
On that furnace the igniter WILL glow with a roll out tripped! The rollouts are in series with the gas valve power! Calm down Harley!
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Old 12-06-2011, 04:10 PM   #10
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Now. On to the problem. A three flash is a pressure switch error caused by a blocked vent or failed inducer or a bad switch. Most if the time it is not the switch. Check your flue and heat exchanger.
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Old 12-06-2011, 04:16 PM   #11
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Goodman Furnace Model Number GMNT080-4


yes the idea is to help get furnace running not to prove each other wrong. if we make a mistake lets hope our partners can adjust it kindly...we all make mistakes.....i agree with yuri,tech126,and harley...lets get it fixed... oh almost forgot my 2 cents...check roll out switches.....jump out to see if valve fires...

Last edited by ben's plumbing; 12-06-2011 at 04:18 PM.
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Old 12-06-2011, 04:33 PM   #12
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Goodman Furnace Model Number GMNT080-4


I think I know Harley from B4 aka acefurnacefixer? defunct for awhile and now resurrected but lost it's traffic hvacmech .com? did thousands of posts there back in the day. reminds me of our friend clover. LOL . No problema.

Goodman does things different than others. most manufacturers put the rollout and limits in series with the circuit board after the tstat energizes. goodman puts it in series with the gas valve just to be different. perfectly safe but adds some wear and tear to the igniter if a limit opens.
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Last edited by yuri; 12-06-2011 at 04:38 PM.
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Old 12-06-2011, 04:41 PM   #13
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Goodman Furnace Model Number GMNT080-4


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On that furnace the igniter WILL glow with a roll out tripped! The roll outs are in series with the gas valve power! Calm down Harley!
I find that hard to buy, but if its true then i will stand corrected and accept my appoligies......I guess given the fact that Goodman (formerly janitrol or as we techs call them junkatrol) is the low baller preferred line I would not be surprised.
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Old 12-06-2011, 04:50 PM   #14
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Goodman Furnace Model Number GMNT080-4


they do have a cute cost effective ( their specialty ) way of hooking up a 24 volt humidifier that no one else has. no need for a 24 v HUM terminal. just put a pigtail wire on the low fire or main pressure switch and supply 24 volts from there. clever eh.

5 brownie points for the first correct reply why that works and the reason for doing it.
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Old 12-27-2011, 10:14 PM   #15
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Goodman Furnace Model Number GMNT080-4


Refer to POST on 12/06/2011 REF: Goodman Furnace Model Number GMNT080-4

I had to have a service tech. come and look at my furnace as I did not have any way to check pressure on the lines. After checking he found that the pressure switch was bad. He replaced it and the furnace started right up. Heat again, YES!

This is a simple repair. The repair company chaged me $110.00 for the pressure switch plus labor. I looked on the internet and the switch would cost you under $30.00. If after checking all the components during troubleshooting and nothing is found, change this switch.

The tech told me that the two components that go out on this model of furnace are the pressure switch and the gas valve.


Last edited by msgbob79; 12-27-2011 at 10:18 PM.
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