furnace GMP075-3 stop working... need help plz.

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  #1  
Old 01-04-08, 01:29 PM
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Red face furnace GMP075-3 stop working... need help plz.

Happy New Year!!

My furnace just stopped firing last night and it's getting cold and cold... we have like 5 F outside...

So I'm asking for any help possible :

The fan is still wokring, it 's making some tick tick noise ( like the solenoid is still working.. ) but there's no flammes. I opened the lower panel and the red led is on.

The flamme sensor and the ignitor seem to be dirty so i
so I took the flamme sensor out and cleaned it up with some steel wool and put it back. Tried it and same thing: fan is on, some tick tick noise, a wispering sounds from gas, the ignitor doesn't change color... and nothing happen next.

The thermostat seems to work fine as it tried to start the furnace.

I have a question:

- Does the ignitor supposed to turn red and light up the flamme? ( if it works )

I'm thinking that the ignitor is broken.

Thx
 
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  #2  
Old 01-04-08, 01:39 PM
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You need to take the panel covering the burner compartment off and observe carefully everything that happens when you turn the thermostat up for heat. You need top report back with your observations.

The make and model of the furnace, which I'm presuming is a warm air gas furnace would be helpful.

Based on your comments, I'm GUESSING that you should see something like the following:


With the thermostat turned all the way down, there is nothing happening at the furnace.


When the thermostat switches the furnace on, you see a small motor start up near the burners, but not the fan that circulated the air around the house.

After that motor comes up top speed, the glow plug ignitor should slowly get white hot over a period of about thirty seconds or so.


You should hear a click and hear the main burner gas turning on. It should light up within a second.


If there is no gas or the gas doesn't light, the ignitor shuts off.



So, what can you tell us about how your furnace is operating?
 
  #3  
Old 01-04-08, 02:00 PM
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Also, look carefully to see what the ticking noise is. While you suggest that you have a furnace lit with a hot surface ignitor, the ticking noise suggests that a spark lights a pilot light which lights the burners in turn.

So--- what's causing the ticking noise? Do you see a spark trying to light the pilot burner? If so, is there gas coming out of the pilot burner --- often you can hear the gas coming out of the pilot.
 
  #4  
Old 01-04-08, 07:03 PM
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Originally Posted by SeattlePioneer View Post
You need to take the panel covering the burner compartment off and observe carefully everything that happens when you turn the thermostat up for heat. You need top report back with your observations.

The make and model of the furnace, which I'm presuming is a warm air gas furnace would be helpful.
Correct, I believe it's a Goodman Furnace. ( or made by Goodman )

Based on your comments, I'm GUESSING that you should see something like the following:


With the thermostat turned all the way down, there is nothing happening at the furnace.
Correct

When the thermostat switches the furnace on, you see a small motor start up near the burners, but not the fan that circulated the air around the house.

After that motor comes up top speed, the glow plug ignitor should slowly get white hot over a period of about thirty seconds or so.
The ignitor does NOT start at this point

*** This suggest that the ignitor may be failing.

You should hear a click and hear the main burner gas turning on.
I can hear the hissing of the gas line feeding to the burner and as the ignitor is not red, there's nothing happened.

Eventually the motor on top of the burners stop and the cycle restart... :meaning:

The motor will start again, some ticklingnoises ( i guess it's from the control trying to fire up the ignitor, then the hissing noise from the gas-line/burner trying to feed the ignitor

*** now at this stage, if i manually fire up with a match, the burners will start and the three burner will fire .... but it only last a few minutes and the flammes from burners shut down. and eventually the cycle restart....

I 'm gonna try to change the thermostats and see what happen after.

Thx again Seattle Pioneer.

*** The tickling noise is just (like the noise from the solenoid) trying to start something ( in this case the ignitor i guess.. ) i believe the sound is normal.
 
  #5  
Old 01-04-08, 07:37 PM
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Is it normal that the burner flamme goes off after 2-3 minutes? and the cycle restart?

Even though it's only 55o in the house and the thermostat is set for 68o

I never really observed how the furnace operated normally so i just don't if it's normal.

The fact that the ignitor fail to go red/white may indicates that I need to get that replaced?
 
  #6  
Old 01-04-08, 08:09 PM
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I am normally not posting at this time, but I JUST got in from working on a furnace from hell. One thing led to another and then my cell phone d/c-a/c inverter went out on me, as I left the address, with my cell phone being dead and messages awaiting me. Besides having to change out an updated ignition control board that required making conversions per instruction manual---Anyway ---

You could have one main problem my furnace just had: Pressure switch not always opening all the way. Sometimes it would, sometimes it would only for a few minutes and then the flame would shut off, and sometimes could not get furnace to reignite. Cause: Plugged up condensate 1/2" CPVC drain and trap. This was affecting the operation of the pressure switch. I had to redo the trap for it, that was tied into the 2" pvc exhaust line, as the trap was full of sand. And all the fittings were glued, and I ended up removing a portion of it and jury rigged my own trap with heater hose and band clamps, making a removable trap.

Bottom line is, you may have a similar sporadic condition, which them will affect the drafting of the furnace, which then in turn affects the pressure switch, due to a back up of unwanted condensate water.

To cure: Disconnect the tubes and blow first from where you can disconnect them at the furnace and blow toward the trap and drain that usually goes into a condensate water pump or into a hole in the floor. Then blow the other direction back into the furnace. You can feel when you are blowing if the line is still clogged or clear. Afterwards you should fil the trap back up with water.

.........

Zigot:
"Is it normal that the burner flamme goes off after 2-3 minutes? and the cycle restart?


The fact that the ignitor fail to go red/white may indicates that I need to get that replaced?"

There is sort of an impossibility here: If your furnace truly cycles and the fire comes on every 2-3 minutes, then the ignitor, of whichever type you have, must be working. Otherwise the furnace could not fire back up again.

Let us know what kind of ignition you have, for sure: The glow kind?; or the spark kind that either fires the burner directly?; or it sparks to light a pilot. (The sparking type issues a series of small sparks yo can see and hear).
 
  #7  
Old 01-04-08, 09:35 PM
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Ecman51 :

The ignitor is the glow type ( a thin piece of metal that glow red/yellow )

I'm positive the ignitor is failing. Like i said: when i turn on the furnace, the motor start, and the ignitor should glow ( but it's not ), then the gas line open but no flamme detected so the heat sensor shut it down. and the cycle restart....

I have to manually light the burners up with a match ( right at that moment when the gas is feeding out to the burner ) then they will burn for like 2-3 minutes then they stopped. Then the cycle restart.

If I don't light it manually, then it will just keep restarting ... motor start up, the hissing sound from the gas, motor stop, Then motor start up, etc.... very consistent.

*** it was working fine until last night. Then I started to notice the temperature is getting colder and colder around noon....
 

Last edited by Zigot; 01-04-08 at 09:55 PM.
  #8  
Old 01-04-08, 09:41 PM
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You still haven't located and described the source of the ticking noise. That still suggests that you may have an intermittent pilot ignition system and the ticking noise is a spark trying to light the pilot.

But everything else you say describes a hot surface ignition system.

If you can't see and identify a hot surface ignitor, you can't repair it by inspecting it for cracks and replacing it. The critical thing for you to do is to spend time locating and inspecting the ignitor for damage, presuming there is one. There probably is, based on your comments.

You may have a second problem with the furnace cycling too often.

It's pointless to replace the thermostat. There is no suggestion that that will solve any problem at this point, and it might cause new problems if you don't install it correctly, a real possibility.
 
  #9  
Old 01-04-08, 09:53 PM
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Originally Posted by Zigot View Post
Ecman51 :

The ignitor is the glow type ( a thin piece of metal that glow red/yellow )

I'm positive the ignitor is failing.
Easy to test and then also easy to replace, if necessary. Do you own a multimeter (often called voltmeters) where you can test it out?

You disconnect the jack connection where often the wires change colors, and then they become braided looking thin white wires heading into the burner. You put one lead of the meter to one connector and the other lead to the other connector, when you have the jack apart and the test meter set to ohms, and if the hot surface ignitor is bad you could get a reading anywhere from about 65-95 (I have heard various figures) on up toward infinity (no continuity at all). A new HSI should be about 22-30 ohms, generally.
 
  #10  
Old 01-05-08, 06:04 PM
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Originally Posted by SeattlePioneer View Post
You still haven't located and described the source of the ticking noise. That still suggests that you may have an intermittent pilot ignition system and the ticking noise is a spark trying to light the pilot.

But everything else you say describes a hot surface ignition system.

If you can't see and identify a hot surface ignitor, you can't repair it by inspecting it for cracks and replacing it. The critical thing for you to do is to spend time locating and inspecting the ignitor for damage, presuming there is one. There probably is, based on your comments.

You may have a second problem with the furnace cycling too often.

It's pointless to replace the thermostat. There is no suggestion that that will solve any problem at this point, and it might cause new problems if you don't install it correctly, a real possibility.
Sorry to make you confused. By the tickling noise, i meant a very quiet click of the relay switch. It's a very short single click noise.

It happened about 30 second or so before the hissing noise of the gas .... ( so i guess the control board turn-on the relay switch to send a signal to the ignitor... )

The ignitor plate seem to be very dirty (i can identify clearly where is the heat sensor and the ignitor - I already took out the heat sensor and clean it with some steel wool )

I'll check again the thermostat again. But I'll try to get a compatible ignitor to replace it first.

So far that's the only part that doesn't seem to work. ( except ONE TIME and failed every single other time )

About the furnace cycling too often ( every 2-3 minutes.. ) -->> suggest that the thermostat may be defective?

What is the normal cycling time by the way?... the burners fire up til the temperature reaches the setting temp? .....

Thx
 
  #11  
Old 01-05-08, 06:10 PM
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Originally Posted by ecman51` View Post
Easy to test and then also easy to replace, if necessary. Do you own a multimeter (often called voltmeters) where you can test it out?

You disconnect the jack connection where often the wires change colors, and then they become braided looking thin white wires heading into the burner. You put one lead of the meter to one connector and the other lead to the other connector, when you have the jack apart and the test meter set to ohms, and if the hot surface ignitor is bad you could get a reading anywhere from about 65-95 (I have heard various figures) on up toward infinity (no continuity at all). A new HSI should be about 22-30 ohms, generally.
The ignitor is connected thru a quick locking connector type, very easy to access.

So in other word, i can just disconnect the ignitor, ( i do have a industrial multimeter type ) and just measure the difference between the two wires in ohms reading right?

The surface of the ignitor looks kinda dirty and roasted ( covered by black stuff )

Is there any way to temporary clean that surface until i can get to buy a new one?

I have to call around on monday to see who 's selling this type of ignitor / or compatible one in town.

I read somewhere that the skin oil will ruin the ingitor surface...( i have latex gloves at home i can use )
 
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Old 01-05-08, 07:49 PM
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I think you'll find that there is no continuity through the ignitor (infinite resistance) when you test it with your meter.


I'm concerned about the dirty ignitor. Is it covered with soot? That would be very unusual, and suggests that the heat exchanger might be sooting up. You'd need to use a flashlight and mirror to inspect the heat exchanger for any indications of black soot. If it is sooted, you should have a service agency clean and inspect the heat exchanger and burners as needed and determine what might be causing the sooting.

I wouldn't recommend that you try to clean the igniter, it's quite deleicate and is likely to break.

You can also test the ac voltage going to the wires for the ignitor. When you hear the tick that you mentioned, you should get 120 VAC to heat the igniter. That's a secondary check which will tell you whether the circuit board could be bad and not providing the voltage needed, rather than the igniter being bad. You can turn off the gas before doing that last test to avoid having a full head of gas coming out of the burners.
 
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Old 01-05-08, 10:11 PM
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Originally Posted by SeattlePioneer View Post
I think you'll find that there is no continuity through the ignitor (infinite resistance) when you test it with your meter.


I'm concerned about the dirty ignitor. Is it covered with soot? That would be very unusual, and suggests that the heat exchanger might be sooting up. You'd need to use a flashlight and mirror to inspect the heat exchanger for any indications of black soot. If it is sooted, you should have a service agency clean and inspect the heat exchanger and burners as needed and determine what might be causing the sooting.

I wouldn't recommend that you try to clean the igniter, it's quite deleicate and is likely to break.

You can also test the ac voltage going to the wires for the ignitor. When you hear the tick that you mentioned, you should get 120 VAC to heat the igniter. That's a secondary check which will tell you whether the circuit board could be bad and not providing the voltage needed, rather than the igniter being bad. You can turn off the gas before doing that last test to avoid having a full head of gas coming out of the burners.
You're correct: my resistance reading came back negative on the ignitor.

I took the ignitor out: it's a 2 mm thick dark piece of some kind of non-metal material ( well feel carbon like material ) .... i thought it's built up by debris but actually it's not. I was fooled by its texture. It looked pretty clean for a 8 year old furnace.

I tried to clean it a bit and put it back but it still not responsive.

ONE time during this furnace break down, i saw the ignitor working!!! So the AC voltage on the wire that feed the ignitor is good.

I guess my next step would be finding a replacement compatible ignitor.
 
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Old 01-05-08, 11:23 PM
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Yes, you need a new ignitor.

My suggestion is to buy two and have one as a spare for the next time.
 
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