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Furnace on the fritz

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Hey all,

In the past few days, my Amana/Goodman furnace has gone on strike. Here are the highlights:

This is a natural gas furnace / electric AC unit. I expect it is original to the house, built in 2007. We've been here since Summer 2016 and had no trouble with heating or cooling. We don't run it too hard in the winter, usually not set higher than 68 (for my hot-natured wife). I use the washable electrostatic filters & switch in a clean one about once a month.

Last week we realized it was extra-chilly, and on Thursday I started trouble-shooting. The thermostat control works to kick the unit on & off. The air handler runs, but air is cool/cold instead of warm. I followed the manual instructions for restarting, and that got me another few days of heat.

Today (Sunday) the warmth is gone from the air again, and the restart process did no good. (Was sort of expecting it to go this way.) I can see that the burners are not igniting (although again, everything else seems to be functioning normally). The LED gives me 4 flashes. I'm pasting in text from the Troubleshooting Chart (I don't seem allowed to attach the photo I took):

Symptoms of Abonormal Operation:
- Circulator blower runs continuously. No furnace operation.
- Integrated control module diagnostic LED is flashing FOUR (4) flashes.

Fault Description:
- Primary limit circuit is open.

Possible Causes:
- Faulty primary limit switch.
- Insufficient conditioned air over the heat exchange. Blocked filters, restrictive ductwork, improper circulator blower speed, or failed circulator blower.
- Loose or improperly connected wiring.

Corrective Action:
- Check primary limit. Replace if necessary.
- Check filters and ductwork for blockage. Clean filters or remove obstruction.
- Check circulator blower speed and performance. Correct speed or replace blower if necessary.
- Tighten or correct wiring connection.

Cautions & Notes:
- Turn power OFF prior to repair.
- Replace primary limit with proper replacement part.
- Replace blower with correct replacement part.


I'm pretty much a novice with HVAC issues (and wary of working on anything with natural gas), so I'm mostly looking for advice in layman's terms of what to expect from a qualified tech. Just don't need to spend money on anything but the necessary repairs.

On the other hadn't, if you guys think I could make the repair myself without much drama, I'm willing to give it a shot.



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 What state do you live in? I was just wondering what temperature is you might be looking at. Some systems with a gas furnace are just a backup for a heat pump. Beyond that I'm afraid I'm not going to be much help.

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I’m in Georgia. Temps have been 30s and 40s here lately, so we’re not going to freeze overnight or anything. We also have a separate system for the basement, so I’ve turned that up a little to help the main level stay warm till it’s fixed.

I do have gas heat for sure. You can here it fire up (normally), plus gas heat just comes out of the register a little toastier than electric, in my experience. 

The other thing is that I could see the burners ignite the other day when I temporarily got the heat back on, but they don’t light now, with the LED fault light flashing. 

Thanks though!

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