Goodman furnace with inoperable status light

[Rocky Rotella]

Before calling in a professional, I was hoping you guys might be able to provide some insight on an issue thats occurring with the furnace in my detached garage.

We moved into a preexisting home about 11 months back. It was built in 2006 and has 720 sq/ft detached garage/shop. The structure is fully insulated and includes a Goodman HVAC system. The furnace is mounted horizontally in the rafters.

The original owner was an electrical contractor. He sold the home to owner B in 2010. They didn’t use the garage for anything more than a storage area. When we moved in during Dec 2016, the furnace hadn’t been ran since 2010. I added new batteries to the thermostat, kicked it on to see what would happen, and instantly had normal operation. The furnace worked fine for a couple of weeks and it suddenly quit producing heat.

Fast forward to this year. I planned to call a professional to give the system a once over. I kicked the furnace on to see what would occur and to my surprise, it began operating normally. After a several days operating normally, it again quit producing heat. I wasn’t able to crawl up there is it was operating to look for status light trouble codes.

If I cycle the unit off with the thermostat, and then select Heat, the inducer motor kicks on and I can manually turn the recirculating fan on too. The status light is dead. I tried resetting with the breaker to no avail.

So what do you think? Would this symptom be characteristic of a bad control board?

 

[Stuff]

If status light never lights/blinks at all then replace the control board.

 

[Rocky Rotella]

Thanks.

It doesn’t blink at all. I’ll have to give that a try.

 

[naturalgas]

It may take three tries to ignite and fail for a trouble code light. Take cover off have someone turn up thermostat and see if you can see the igniter glowing? If it does and starts up then quits it could be simple clean flame sensor. If no igniter glow, pressure switch ports could be clogged up. Normal operation is thermostat call for heat, inducer motor starts up, pressure switch closes, igniter glows. Main gas valve opens, flame sensor sensors burner on. After short time blower comes on to circulate heat. Don’t just jump to replace board. If it comes on intermittently for you, I don’t think that is the problem . Could be but other things to check first. Good luck



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[Rocky Rotella]

Thank you. I kicked the thermostat on and didn’t hear any ignition attempt at all.

Would pressure switch operate intermittently?

 

[JRC3]

Yep, start with the basics. KISS!

First, check the fuse on the board if you're getting no status light.

Never clean a flame sensor with any chemical or anything abrasive. Use something like a soft cloth or best bet an old dollar bill. Seriously, an old bill is recommended.

CHECK THE FILTER and replace it even if it's new or it looks clean. If it hasn't been used in years a brand new filter could clog up almost instantly. )I am speaking from personal experience.) Best bet, take it out for diagnosis and then proceed with the filter if things go well.

Check the flue. Make sure the rain cap is in place and has mesh or something to keep out birds and rodents. Also check for insects.

Check that all the limit switches are connected. Maybe a connector came loose or a mouse chewed a wire.

This guy's YT channel is awesome. I've learned many things from him.

Lastly, good luck.

 

[JRC3]

Oh yeah...

The fuse on the board will be an automotive type fuse.

Then get out your volt meter and check for power going into the transformer (120V). Then check for power coming out. (Should be 24V)

 

[naturalgas]

Thank you. I kicked the thermostat on and didn’t hear any ignition attempt at all.

Would pressure switch operate intermittently?

Make sure your thermostat is good. check with continuity or jump out at board. Yes pressure switch will operate intermittently if port is partially plugged. Take off hose at heater and run a thin piece of wire thru it. You will feel if plugged should run thru port easily no resistance. As stated make sure air filter is clean. If filthy could be off on limit switch. Check that for continuity. Check roll out safety switches same way. If everything checks ok and it started a couple times for you, replace the board it’s no good


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[Rocky Rotella]

Thanks for the great advice, guys!

Late last evening I was able to crawl up into the rafters and begin some diagnostic work. My ceiling is 12+ feet tall and had been using a 10-foot A-frame ladder to peak up there. I was able to get my extension ladder out to reach it.

As soon as I pulled the side covers off, I was impressed with how clean everything was inside. I was able to confirm that the unit is Goodman GMS80453ANA that's mounted horizontally. I closed the door switch and immediately saw the glow of the status light. It was blinking three times. It was so far back in the unit, unfortunately, that I couldn't see it illuminating through the sight-window when I was looking up there with the cover on, particularly at the angle it sits. I'm used to them being brighter. I know now better.

I pulled the pressure switch vacuum hose and the end that connects to the inducer motor barb was a little loose, but it definitely switched on and off when vacuum was applied. I applied a constant vacuum source and what do you know, the furnace lit off immediately!

I grabbed a stiff piece of wire and poked it through the barb and you could feel the blockage. I knocked it loose, trimmed about 1/4" off the vacuum hose, reconnected the switch, and reinstalled the side covers. As of 10PM it was a balmy 60 degrees out there, running right at the stat.

Thank you guys!