Help with Goodman furnace - Short Video

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  #1  
Old 05-15-19, 07:24 AM
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Help with Goodman furnace - Short Video

Hello!

My Goodman heater, installed in 2009, is not working.
Model #GMH950904CXAB

Burners come on, exhaust fan comes on, then shuts off.
Red light on circuit board in front of main fan blinks 4 times. This board is an Emerson Technologies board. To the left of the red light is "DS1" and to the right of the red light is "SW2". To the right of that is a Fault Recall button.

Here is a short 3 minute video:
Awesome Short Video

Thanks for your help!
 
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  #2  
Old 05-15-19, 10:48 AM
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Update:

4 blinks means "Open Limit" - found the codes on the back of the panel and found youtube videos.

I had replaced intake filters when I first had an issue so it can't be that.

I removed the limit switch and tested it with a multimeter and a lighter - seems to work fine.

I replaced it and tried the heater again and it shut off like before - and 4 blinks.

So it is hitting the high temp limit and shutting off. The blower never comes on.

What do I check next?

Thank you!
 

Last edited by bradleydgood; 05-15-19 at 12:17 PM. Reason: typo
  #3  
Old 05-15-19, 12:04 PM
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Update:

By watching other youtube videos, I found a second limit sensor/switch above the blower. When this has no continuity and is concave, I get 4 blinks - open limit.

When I reset this to have continuity, and start the heater, it acts like in my video, and shuts off, and then tests as no continuity. And I get 4 blinks.

So at least I know what sensor is causing the trouble code.

So why is that sensor being tripped? And why is the blower not starting up? Maybe the sensor is being tripped because the blower is not starting? How do I know my blower is good? What would be the next step to diagnose this?

Thanks for the help!
 
  #4  
Old 05-15-19, 02:34 PM
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Welcome to the forums.

You need to confirm that the blower is indeed running and properly. If it's not.... a limit can open to keep the furnace from overheating. There can be up to four limit switches on furnaces.
 
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Old 05-15-19, 04:49 PM
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In the picture are shown three limit switches. Two claim to be manually resettable and one automatic reset. Some times the automatic type are used at all three locations. Those three switches form a series loop and appear on pins 1 and 7 on the main board plug. I've highlighted the wire colors. That circuit should always be closed. If it opens you'll get the four flash code. You need to identify which one is opening and in what location.

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