Furnace Intermittently Won’t Fire Up [Video]

WayneJetski

Hey all,

I’ve had this issue on and off for over a year. It seems to creep up at the worst times (when temps drop significantly in the winter). It’s a Goodman gas furnace converted to use propane. It’s only 3.5 years old.

I’ve had the gas valve replaced. It still came back. I had them come back and adjust the pressure, said they didn’t bump it up to the correct pressure for propane. Now it’s still having issues. Last time it happened, I cleaned the flame sensor, the burners and the HRV unit.

Furnace filters are changed regularly.

Sometimes it starts working again for a month before the issue returns. 

Please check out the video I recorded:

https://youtu.be/rdC6614Efsk?si=-Kq3nI26Lbd0F467

I’m losing my mind! Does anyone have any ideas on what to debug next?

I ordered a new flame sensor to replace tomorrow.. but it’s not staying lit for 3 seconds as shown in the video. 

Thanks for reading and watching.

109A_5

Hello @WayneJetski,
With the information that was in the video and no model number of the Goodman, I would say there is something wrong with the control board (if it has one) or a loose connection in the wiring path to the gas valve. Sounds like the Gas Valve is not held energized in a consistent manner.

Probably not a long enough flame duration for flame proving.

I would start by measuring the 24 VAC at the gas valve and see if it is steady when the flame drops out. I bet it is not.

WayneJetski

Thanks for the quick reply @109A_5. I’ll look into that shortly. Much appreciated. 

mattmia2

has a competent tech looked at it when it is happening? has the pressure been checked when it happens to make sure a regulator isn't freezing up or the tank doesn't have enough capacity at that temp and draw or other things like that?

HVACNUT

It was converted to LP gas. The gas valve was replaced with a new LP conversion kit, right?
When the furnace was originally converted, the orifices were replaced, right?
Are you considered high altitude?
It certainly sounds electrical. The valve doesn't even stay open long enough to not sense flame. It's a 2 Stage gag valve. Is everything wired that way? 2 Stage thermostat, or is W1 and W2 jumped out at the control board.
Make sure all grounds are secure. 
Can you post a pic of the wiring diagram?

WayneJetski

The temperatures became mild but it still happened again today. It was working fine after recovering on its own since my first post. It’s very strange how intermittent the problem seems to be.

Here are a few more images to show more details.

Do these details change anyone’s thoughts?

109A_5

Hello @WayneJetski,
You may want to read through this recent thread, seems to be a very similar situation and also a Goodman furnace.
https://forum.heatinghelp.com/discussion/196318/goodman-gas-valve-voltage-is-erratic

My opinion is the same. It sounds like the Gas Valve is intermittently dropping out. You, a skilled friend or a HVAC Tech (skilled in electrical control troubleshooting) needs to do some troubleshooting to determine what is going on and provide troubleshooting direction. As I stated before I would test the 24 VAC at the Gas Valve to start, divide and conquer. I might even use a 24 VAC test lamp to determine if the power to the gas valve is dropping out when it should not be, it may make it more visually obvious. There are many connections, safety limits, relays, etc. between the transformer providing the 24 VAC and the Gas Valve, any one of them could be intermittent with ambient temperature agitating the situation.

mattmia2

The manifold pressure shouldn't be a range,, it should be what was set with the combustion analysis. I'd just connect a 24v lamp or an led with appropriate resistor across the gas valve so I can see when it is energized. I still suspect it is a gas supply issue from your video.

SuperTech

I've had issues with Goodman/Amana/Daikin two stage furnaces doing what you described.  The problem was condensate drainage from the flue pipe. They have had issues with a defect in the rubber 90⁰ elbow that connects to the inducer.  Some of these elbows have a little rubber "lip" on the inside that prevents condensate from draining into the trap and causes excess condensate to drain into the secondary heat exchanger and it causes the pressure switch to chatter.  The furnace won't show a fault code when this happens. 

HVACNUT

What's the "Front Cover Pressure Switch"? It's in series on the Common side from the gas valve to the 12 pin Molex. Is it sealed combustion? If there's a poor ground (Common), or the Door Pressure switch is twitching, it could whack out the valve like that. 
Shut off the power. Make sure all wires going into the Molex fitting are snug. Check and tighten all connections and grounds.
Can you post a pic of the burner compartment? I want to see the Door Pressure Switch.