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Old 12-26-2010, 03:46 PM   #1
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Help Needed. Goodman furnace


It broke down at the worst time possible, christmas eve. It's been two days and it started snowing this morning. I am going to find someone tomorrow if I have to. I've been trouble shooting since last night. And here's some info:

1. Furnace: goodman gmpn 100-4 rev B
2. Symptoms and what I've tried: furnace not coming up. I had to switch on/off using the external emergency switch to force it to start. Blower started. Then gas gushed in as I could hear a clicking sound then a hissing sound and a faint smell of gas. But the burner didn't light. The unit tried 3 times and shut down. I had to then switch off the external switch and back on to force it try again. Noticed that ignitor (on the left side of the burner) didn't do anything. Searched on the internet, it was supposed to glow red. I tried to poke it with a screw driver. It glowed red once but didn't stay long enough for gas to come in.
3. What's my plan: Buy a new ignitor and replace it tomorrow. But not sure if it will fix it. What else I need to try?

Any advice will be appreciated. Thanks!

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Old 12-26-2010, 03:48 PM   #2
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Help Needed. Goodman furnace


in blower door window do you see a led flashing a code after it has failed to run? Do you have volt/ohm meter?

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Old 12-26-2010, 04:00 PM   #3
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Help Needed. Goodman furnace


I am going down to basement now to check it out... I don't remember seeing though any flashing light... Will be back in a sec.
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Old 12-26-2010, 04:13 PM   #4
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Help Needed. Goodman furnace


hmm, I don't see any led light outside the unit. My unit is about 11 years old. Maybe it isn't equiped with it. I do have a ohm meter. btw, is it safe to ignite the burner manually? someone mentioned it in a different thread about manually start it. I want to give a try.
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Old 12-26-2010, 04:19 PM   #5
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Help Needed. Goodman furnace


Quote:
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hmm, I don't see any led light outside the unit. My unit is about 11 years old. Maybe it isn't equiped with it. I do have a ohm meter. btw, is it safe to ignite the burner manually? someone mentioned it in a different thread about manually start it. I want to give a try.
led would be viewed through window in blower door if you have a led, not on outside of unit. disconnect the ignitor. check resistance of the ignitor. should be less then 200 ohms. spec is 50-90.....but have seen them still work up to 200+. you can light the burners manually if you know what you are doing. wait until you hear the gas valve open. use something that gives you some distance from the burners incase of flash back. This furnace is know to have cracked heat exchangers. You should have it checked by a pro for this condition. I DO NOT recommend manual lighting the furnace unless you know what you are doing!
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Old 12-26-2010, 04:34 PM   #6
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Help Needed. Goodman furnace


I did see a clear plastic circle door, the size of a quarter on the blower door. But there is nothing behind it... Interestingly, on the reverse side of the blower door, I did see instructions on how to diagnose by reading the number of blinks of the led. But I just cannot find the status light behind the blower door. Directly behind the circle window on the blower door is just sheet metal. I did see kinda a red led light on the circuit board. But it isn't viewable thru the circle window nor it blinks after the unit fails.

There is burn mark on the ignitor. I'd imagine that it definitely needs replacing, right?

I bit the bullet and manually ignited the burner by using a bbq ignitor. Boy, my hand was shaking...
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Old 12-26-2010, 04:42 PM   #7
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Help Needed. Goodman furnace


most likely, yes, the ignitor needs replaced. there is probably a shield over the control board blocking your view of the led on the board. well if everything lit ok with the lighter then you know how to do it now. be cautious every time. I still highly suggest having that furnace inspected due to Heat Exchanger failure
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Old 12-26-2010, 05:22 PM   #8
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Cool. Thanks... Where is the control board? Is it the circuit board at the bottom half of the furnace unit? There are two panel doors I can take off. Behind of the top one, there is the gas control knob, the burner and the blower to blow the exhaust to the outside of the house. Behind the bottom one, there is a circuit board and big blower that circulates the air inside the house. Is the circuit board the control board you refer to? It is pretty much naked

BTW, what is the heater exchanger? Is it viewable? Can I visually inspect it myself?
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Old 12-26-2010, 06:02 PM   #9
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The heat exchanger is held together with compression rings. Take the blower assembly out and there's usually parts of the rings sitting there. If not get in the furnace and look up at the heat exchanger, check each ring for cracks.
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Old 12-26-2010, 06:36 PM   #10
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Ok... I will replace the ignitor first as it definitely is shot. Will check the heat exchanger if that doesn't work. I also found the status led light on the control board. It is always off though.
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Old 12-26-2010, 07:11 PM   #11
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Quote:
Originally Posted by jzw View Post
Ok... I will replace the ignitor first as it definitely is shot. Will check the heat exchanger if that doesn't work. I also found the status led light on the control board. It is always off though.
1st. do replace the ignitor. 2nd. regardless if the ignitor solves your problem have the heat exchanger checked by a pro. 3rd. the led is off because you are probably viewing it with the door off and have in turn killed the power to the unit through the door safety switch.

IMPORTANT: Don't take for granted that the heat exchanger is ok because your furnace is operating. Have it checked. You will probably not know what you are looking for or what you are looking at.
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Old 12-26-2010, 07:42 PM   #12
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Help Needed. Goodman furnace


Thanks! I just found the led light labeled as status on the board. And based on its position to the circle viewing window, I realized I needed to view it from the 1 o'clock position. Ditto to the door safety switch. The panel had to be on to view the light. What I did was holding the switch down manually and starting the sequence, surely enough I saw the status light flashing with 1 blink at a time. So it was an ignition issue. How much do you think it would cost to have someone inspect the heat exchange? And how do I find a reliable plumber?

BTW, thanks for all the great input
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Old 12-26-2010, 08:04 PM   #13
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Help Needed. Goodman furnace


a furnace inspection should be around the $100 mark and may include a cleaning. BBB is a good place to start when looking for professionals. a good replacement ignitor that I have seen at the home depot and other home improvement stores is the Honeywell universal ignitor. It does not look like your current ignitor, but comes with brackets that will work and is a better quality ignitor and less fragile.
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Old 12-26-2010, 10:31 PM   #14
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wow, I will definitely check it out tomorrow at home depot. Was wondering where I can get OEM or aftermarket ignitor. Hopefully I can get to home depot or any heating supply store as we have more than a foot of snow already.
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Old 01-01-2011, 11:21 PM   #15
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Help Needed. Goodman furnace


hvactech126, thanks for much for your info on the honeywell universal ignitor. I called on monday some goodman dealers and none of them sells parts. And most heating supply stores were closed due to the snow storm. I headed out to homedepot and bought the universal ingitor. It worked like a charm. Thank you so much!

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