# Goodman GMP100-3 Forced air furnace



## allan (Jan 7, 2006)

sylvia said:


> Hello,
> 
> I have goodman gmp100-3 forced air furnace and it is not puttin out warm air. It blows air but each time it tries to ignite it lights for a few seconds then goes out and it keep doing that but never light the blower just keeps going. Does anyone have an idea of what might be causing it not to ignite ?


 At the top of your burner section there is a flame sensor.
It is a rod metal rod with ceramic around it.
It has one wire coming from it.
Remove the sensor . get steel wool, not sandpaper.
Clean the rod section.
Put back together.
This is an easy fix.
But remember to get your furnace serviced as there is a reason that you have a build up of crap on the sensor.
Good Luck

Allan
Clarkson Comfort Zone Heating & Air Mississauga

weinstall.ca


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## nvr2low (Feb 15, 2007)

i have the same furnace and my light is blinking 3 times. it says that its a pressure valve issure. i know nothing about gas, i checked to make sure the exhaust vent is clear so im pretty sure the gas is not getting there. any ideas? the gas is getting to the hot water heater that is about 6 feet away on the same feed. I need help or its going to be a cold night.


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## rakes9720 (Dec 13, 2006)

There is a pressure switch near the inducer (about a 3" diameter circle with at least 2 wires and a plastic tube running to it) that checks to see if the inducer blower is running and if the air is flowing through the heat exchangers. Does the inducer motor come on? If so, put a volt meter across the pressure switch terminals. If it is working there will be 24 VAC across it when the furnace comes on and when the inducer gets up to speed, the switch should close and the voltage will drop to zero. 

If there is never any power, check all of the wiring to the switch. Also check the voltage from both wires to ground. At least one should have 24VAC when the furnace is on. 

If there is constant 24VAC then you might have a restriction in the vent or pressure switch tube, or you might have a bad pressure switch.

Post what you find.
Kyle


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## nvr2low (Feb 15, 2007)

well, turns out the exhaust wasnt clear. a bird flew down my chimney and was stuck up against the fan. after posting this i decided to pull the pipe off to make sure it wasnt an exhaust problem and when i looked down there was a bird head poking out of the fan. i pulled it out and its now working fine.


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## altfour (Mar 9, 2009)

*goodman gmp100-3 forced air furnace*

My furnace will not stay running. Everything will start going fine, furnace will ignite with no problem, both blowers turn on, will run for about the exact same time each time, then the little switch on the top of the burner will trip (little nipple pops up). The light will then flash once repeatedly. I will then have to depress the nipple on the little button looking thing to get it to ignite again. What is the cause and how can i fix this?


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## HvacWiz (Nov 24, 2006)

*Sounds like you are reseting the flame rollout switch, probale cause is a cracked heat exchanger I would shut the furnace down and call someone ASAP to have it looked at.*


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## kenmac (Feb 26, 2009)

sylvia said:


> Hello,
> 
> I have goodman gmp100-3 forced air furnace and it is not puttin out warm air. It blows air but each time it tries to ignite it lights for a few seconds then goes out and it keep doing that but never light the blower just keeps going. Does anyone have an idea of what might be causing it not to ignite ?


 

Just to add... could also be a vaccum switch issue, stopped up vent,vaccum at the exhaust motor


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## jenden (Dec 18, 2009)

*Try this*

I have the Goodman gmp 100-3 and I have a problem with my stack. what is going on is that is when my furnace turns on it let's out a little gas smell out that travels out though the top of the water heater vent then it sucks it up. I'm wondering if my water heater inlet and burner needs to be cleaned out or the something else. it started happening around March of 09'


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## jenden (Dec 18, 2009)

sylvia said:


> Hello,
> 
> I have goodman gmp100-3 forced air furnace and it is not puttin out warm air. It blows air but each time it tries to ignite it lights for a few seconds then goes out and it keep doing that but never light the blower just keeps going. Does anyone have an idea of what might be causing it not to ignite ?


I have the Goodman gmp 100-3 and I had that problem before. Adjust your igniter(glow rod) closer to the flame. Make sure your furnace is turned off from the breaker if possible first. Not to much or you'll burn it out. The igniter is also a sensor that sense if the flame is on. When the igniter can't sense the flame, it turn on then the gas valve opens then cloes because it doesn't sense a grounded connection(electricity) between the gas ports and the igniter. Yes, electricity travels though the flame. Try this before you call out someone :thumbup:


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## beenthere (Oct 11, 2008)

jenden said:


> I have the Goodman gmp 100-3 and I have a problem with my stack. what is going on is that is when my furnace turns on it let's out a little gas smell out that travels out though the top of the water heater vent then it sucks it up. I'm wondering if my water heater inlet and burner needs to be cleaned out or the something else. it started happening around March of 09'


Common on that type of set up. Comes from a cold chimney.

Did you set your water heaters temp lower last year some time.

Also could be a restricting chimney. And its draft increases as it gets warmer inside the chimney.


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## jenden (Dec 18, 2009)

beenthere said:


> Common on that type of set up. Comes from a cold chimney.
> 
> Did you set your water heaters temp lower last year some time.
> 
> Also could be a restricting chimney. And its draft increases as it gets warmer inside the chimney.


Is there any way to clean the inside from the top vent of my gas water heater down to the burner. If so how and with what?


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## beenthere (Oct 11, 2008)

The problem isn't inside your water heater. Its in your chimney.


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## mast (Dec 31, 2009)

altfour said:


> My furnace will not stay running. Everything will start going fine, furnace will ignite with no problem, both blowers turn on, will run for about the exact same time each time, then the little switch on the top of the burner will trip (little nipple pops up). The light will then flash once repeatedly. I will then have to depress the nipple on the little button looking thing to get it to ignite again. What is the cause and how can i fix this?


Mast: I am just responding way to late , hope this may help someone with similar problem. 

This is mostly due to build up on your flame sensor , your flame sensor is on left side of furnance after your remove back panels, its a metal rod hanging down towards furnance ignition. Just lightly wipe off that rod with sand paper or wool cloth. You should be fine

Buildup on metal rod may be due to some issue with your gas line or you have not serviced your furnance for couple to few years 

Hope this helps


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## SKIP4661 (Dec 3, 2008)

Huh?????????????????????????????????????????????????????????????????


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## nvr2low (Feb 15, 2007)

ok, back with a new issue.

so i have an intermittent issue, the house seams to stay at the temp but every once in a while my furnace wont work until i reset it and right now that is not fixing it. the fan turns on, the igniter turns on, gas doesn't light. cycles 3 times then shuts down and blinks one time. once in a while the gas will ignite for a couple seconds then shut down with the same error. I am at a loss with this one, i cleaned the flame sensor but that is obviously not the issue because the flame is not turning on.

any ideas before i have to spend more moeny than i can afford to have a pro look at it?


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## kenmac (Feb 26, 2009)

Use VM to see where your loosing 24v. If it's firing up & going out . it's not sensing flame causing it to go out. or your loosing 24v to the gv from another source


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## nvr2low (Feb 15, 2007)

well i was probing around the valve looking for the voltage and it fired up and is working now. wondering if the connection is funky even though it looks ok. guess i need to schedule a tune up.


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## kenmac (Feb 26, 2009)

have you had the connections off ? do they feel loose ?


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## nvr2low (Feb 15, 2007)

took them off, they are fine. i do electronics for a living so that i am sure of. it is running fine now, has been on and off for the last hour and a half with no issues. i think i just need to schedule a cleaning since i don't really know how to do it my self and i am a bit nervous messing with gas.


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## jenden (Dec 18, 2009)

Does anyone know the CFM of a GMP100-3?:notworthy:


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## crub (Dec 17, 2011)

I am so glad i found this!!! I did exactly what ALLAN said about the flame sensor and it worked on my furnace. Thanks!!!!!


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## harleyrider (Feb 20, 2007)

jenden said:


> Does anyone know the CFM of a GMP100-3?:notworthy:


That depends on what size blower is attached to the furnace, normaly its 2 and a half or 3 ton


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## beenthere (Oct 11, 2008)

The 3 would indicate 1200 CFM.


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