Furnace won't turn back on after lowering the temperature, what to check?


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Old 03-11-19, 09:01 AM
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Question Furnace won't turn back on after lowering the temperature, what to check?

This is a fairly new Goodman forced air furnace.
I replaced it in 2014 or end of 2013.
All our bedrooms are upstairs where it gets pretty warm even when it's cold outside without heater.
We hardly need any heat at night so I reduced it yesterday to 60 for the night time.

However, when I woke up, the temperature on the first floor was 53 so I checked the thermostat and it's at 60 but heater is not running.
I tried turning off/on several times, increased temperature, reset thermostat etc... but nothing.
I turned the fan to On instead of Auto and I hear fan is running but no fire in the furnace.

What to check? Is thermostat bad?
Is there a way to test it by jumping the wires behind?

I read filter and fuse can also cause this issue.
If fuse is out, fan wouldn't turn on right?
Is the igniter bad?

I want to check few things I can before calling professional help as they are pretty pricey, specially when it's cold outside.
thanks for suggestions.
 
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Old 03-11-19, 10:31 AM
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Are you getting any error codes?
 
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Old 03-11-19, 02:33 PM
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Thermostat looks normal.
There's no display for errors on the furnace.
 
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Old 03-11-19, 03:47 PM
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Check line/load voltage with your meter.
If correct check transformer output.
If correct check for a call for heat.
 
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Old 03-11-19, 04:03 PM
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If it's a newer Goodman gas furnace.....it will have a sight glass in the blower door. Look thru it to see the red flashing light. Count the flashes for the fault code. A model number would also be helpful. You'll find it on the side wall near the burner.... behind the burner service cover.
 
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Old 03-12-19, 09:13 AM
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Unhappy Broke the ignitor

Yes I noticed that glass hole to check the light too late.
Edit: Model is GMS81005CN
This is what happened.

When I turn on the thermostat, I hear fan but no fire.
Online articles mentioned to check the fuse and ignitor.
15amp fuse has continuity..
Ignitor resistance checked 444 ohms so that was also good.
However, ignitor was white towards the end so I thought of cleaning it.
It was very brittle and broke.



So whether it was the issue or not, I have to replace it.
None of the local stores have it. I ordered it online and it won't be here before Friday.
I'll check for light status after I get the ignitor.

I have 3 space heaters and will get few more today.
Local stores don't even carry heaters anymore, it's only March.

thanks
 
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Old 03-12-19, 09:22 AM
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roughneck77
Check line/load voltage with your meter.
If correct check transformer output.
If correct check for a call for heat.
How do I check those?

Here's the picture of the furnace innards:

 
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Old 03-12-19, 01:05 PM
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I wouldn't worry about checking the supply voltage. If the fan comes on.... you've got power.
There won't be any power with the blower door open due to the safety switch.

Those igniters heat white hot and are very brittle. They cannot be touched or cleaned.
You probably have one in your oven too. Same deal.

If on a call for heat the draft inducer starts but the igniter doesn't glow..... that would most likely be a pressure switch problem. A fault should flash on startup.
 
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Old 03-20-19, 08:20 AM
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Ignitor is not the problem, it's pressure switch stuck open

Got the new ignitor.
Installed it and turned it on.
Same thing as before, fan comes on but no fire.
That means I broke a perfectly working ignitor.

Red LED blinks 3 times.
Pressure Switch Stuck Open.

It could be the switch or it's not getting the pressure from the hose.
 
 

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