Goodman Furnace Gas Valve Not Opening

[webneb]

Need help troubleshooting a new installation of a Goodman 70K btu 95% efficiency two stage gas furnace (Model GMH950703BXA). Brand new. Replaced old furnace with new. Unit ran fine for about 30 minutes and then cycled itself off. No flashing diagnostic light until tried three times and then single diagnostic to indicate three failures and that gas not being delivered to burners.

Gas pressure fine. Unit cycles on, blower runs, igniter heats up but after 15 seconds igniter turns off because flame senses nothing. Not sure why it will deliver gas to burners anymore. I checked the gas valve while running, after igniter heats up, I can confirm valve does not open. I know valve is not the broken because I took valve from another new unit and still same results. In fact, tried replacing every part except the combustion fan

The only thing I can think of is that we did not do the direct venting. While testing, left air inlet as is and combutsion out was vented to existing flue from old furnace (4" flexible tube).

If venting was the issue, wouldn't the unit at least burn for a time and then cycle off ? Now cannot get any gas to be released by valve to the burners. Tried turning off gas, shut off gas valve, shut off electricity, and re-started everything again, but same results. Tried

4 or five more times.

Any suggestions would help.

[Speedy Jim]

You tried a gas valve out of another new unit?

Did you try another control board? (Maybe I missed that...)

Does the pressure sensor close after the inducer runs?

I gather this is some temporary setup with venting. Don't see how that would affect it.

Is the electric service to the furnace control properly Grounded AND is the polarity correct? (Wh Neutral, Blk Hot) The control is very sensitive to those conditions.

Jim

[Stormin Mormon]

Is the gas valve getting power during the ignitor warm up? If so, you likely have a bad gas valve. If not, I'd look for some notes about how many amps the HSI draws. I worked on a unit that had a HSI that glowed nicely, but the amperage draw was wrong. So, the valve didn't think the HSI was working properly.

[bubbabubbs]

I had the same problem a coupla months ago with my 90K BTU Goodman 95%

2-stage furnace. The contractor installed the brand new unit, and after a couple of days the furnace started behaving just like yours is. I called the guy, he came back, opened up the front cover, looked inside, but wasn't sure what it was, but somehow got it to work. Over the next few weeks the problem reoccurred a couple more times, once or twice it self-healed, but then it wouldn't come back on, so I called the guy again. The second time, hew finally figured it out, and was able to fix it. The furnace has been working fine for 4-5 weeks now. Here's what it turned out to be:

If you remove the front cover, there is a black rubber hose inside, about 5/8" thick, that is used to remove H20 condesation (from the exhaust) and drain it out of the furnace (thru a pvc pipe.) Well, this black rubber hose was originally about 2+ft long(orig. length "out of the box long"?), so it was "bent and curved" by 180 deg inside the furnace when installed. There was a section of the hose that was forming a slight U-shape, and it seems that some H20 was just sitting in there instead of being drained out. That's at least how the guy explained it to me, and he thought that, for some reason, was causing the furnace to go into lockout.

Solution: The guy used a pair of scissors/cutters to trim the rubber hose to the total length of maybe 10 " and ran it to the drainage opening (on the right-hand side of the furnace) in a pretty much straight, slanted line.

I hope I am explaining this clearly enough. I was getting so pissed and frustrated for a few weeks, and wouldn't want anyone else to have to go thru the same experience.

Please post an update as to whether you were able to get your furnace fixed. I'll be very curious.

Good luck!

[Bob]

I had exactly the same problem. I had tried everything I could think of. Finally I called the installer since the furnace was only 3 years old and still under parts warranty. He was scheduled to come out the next day. While I was waiting for my wife to dress to go shopping I decided to do an internet search and found this write-up. After reading about the condensation drain hose problem it referred to, I went and squeezed the hose over its entire length since it was very flexible. I then made sure the hose had a drain slant (i.e., no dips) over its length. I estimate that about a pint of water drained when I did this. After that I turned on the furnace and it worked like a charm (at least so far). Thank you for your input!

[hrhofmann]

I wonder if the fact that the hose was clogged with water had somehow an effect on the overall air flow araoudn the unit and that was the problem.

[clare]

Nope - it just threw the pressure balance off and one of the safety "sail switches" would not turn off or on - preventing the unit from firing.

[Art Todesco]

I had an Amana high efficiency unit in my previous house and it had a similar problem. Because the combustion air on this model is from inside the house (basement), it would pick up any dust, etc. in the air. This particulate would then form what I referred to as slime balls inside the drain tubes. There were 2 drains, one from the combustion blower and one from the secondary heat exchanger. Usually the one from the blower would clog. Initially it would start and run for a really long time before combustion. Apparently, it would have to slug enough water away from the blades in order to get enough negative pressure to then allow the gas valve to open and start. If you let it go for a long time, eventually, it would never open the gas valve; only the combustion blower would run. I found that, because of the basement layout, when the furnace was installed, I had to change the side where the drain was located. So, there was a small coupling in the drain line. The line was PVC with a short rubber hose on each end. Apparently, the roughness inside the solid pipe, where the coupling was located, was enough to catch the 'slime balls' and would build up until the line was clogged. I changed out the drain line to a single clear plastic line. Now you can actually see if a clog was forming. But, because there was no roughness inside, it never did. However, I would periodically take out the drains and clean any deposites with a small bottle brush and lots of water.

[phlippin62]

I just now went out and with a length of old hose shoved it down both exhaust pipes if you will and works like a dream.

[Tony Hwang]

What about condensate drain? If in lpock out mode, it takes I think 2 hpours before you can start the unit again. You can rest the unit by turning power on/off. Control board has test point to ground to test the unit. Tried or cleaned flame sensor?

[makolber]

even those of us using Google Groups can see the dates of a post.

Mark

[Tom]

Bob ... You are a genius. How you determined that the problem was the hose filling up with water is beyond me. I disconnected the hose which had a sli ght "belly" in it, drained a half pint of liquid, shortened the length of t he hose, and reconnected it... making sure it was on a continuous slant dow nhill the entire length. Furnace worked like a charm ! I was curious why the furnace worked all last winter but I figure it was in itially installed in the dead of last winter when there was low humidity. t he condensation never built up until I started it up this year. Thanks aga in. Tom

[Tony Hwang]

Our furnace is Carrier 96% model. No hose. Rigid PVC small dia. pipes connected to AC evaporator pan drain then straight down to drain in the basement floor. No such problem either on AC or furnce. I bet the problem will recur unless you make sure same standing water problem happens.

[promedic92]

2017 --- Installed a brand new Goodman Furnace/Central Air system last summer and had the SAME experience as you. I found this blog and fixed it. Thank everyone!

[ChuckE]

replying to bubbabubbs, ChuckE wrote: Thanks for your posting. I was experiencing the same thing - the gas burners would not kick on. This was just a few hours after they had done their annual service check. Service came back out and he first said it must be the thermostat since the furnace was working when he left. He then determined it must be the gas line. Then the gas valve. Finally he got on the phone with his head technician. He began checking everything he had already done. I step inside the house to warm up and I googled and found your experience. I went back outside and the technician, still on the phone, was discussing going through all the wiring to find the problem. I reached up and gently lifted the hose and it began to drain. The tech was heading back to his truck for more tools when I flipped on the power switch and the furnace kicked on. It was so funny when I yelled back to the tech that I had fixed the furnace. He hung up the phone and came to see what I was talking about. In the end the tech thanked me and said I saved him a lot of time and trouble pulling the wiring apart to test. He then said he learned something today. He learned that he should google things first. He did get the hose adjusted so it drains properly and all is well.

[trader_4]

The root cause of this problem is very likely that it was not installed correctly. Gas furnaces are typically shipped so that the venting and draining can be done on either side. So the hoses are shipped longer, so that if needed, it can be switched to the other side. I think my hose was unattached with instructions to cut it to the required length. I bet some installers don't cut it, or don't route it correctly, etc. In your case, the service guy probably moved it while he was doing his other work, creating a situation where it won't drain. And I'd say his problem isn't that he needed the internet, it's that he doesn't understand the basic operation and how to diagnose. Doesn't that furnace have blinking LEDs and codes on the door to show what the problem is?

[Tekkie®]

ChuckE posted for all of us...

Reading your post was draining to my soul.

[Bob]

replying to Stormin Mormon, Bob wrote: I am having this same problem. Replaced the circuit board and wiring harness to no avail. I was told by several HVAC techs that the circuit board receives no feedback from the HSI. I changed out the HSI. The HSI does glow but will not fire on the first attempt......sometimes it does. It is not the rollout switches because I checked for voltage straight out of the board before the switches. No

24vac until the second lighting attempt. Please help, this problem is driving me crazy

[trader_4]

If the valve solenoid is shorting out, the board could be trying to put out 24v, but can't raise the voltage. Still you'd think you would see some vol tage at the solenoid. Could also be a pressure switch, but then you wouldn' t think the igniter would glow. What code is the board flashing when it fai ls?

[Tekkie®]

Bob posted for all of us...

Hey Bob, Stormy is in the great HVAC system in the sky.