A couple of furnace questions

[HighUintas]

I don't personally know any HVAC guys and I live in a city, so when they come check my furnace they just try to sell me a new one. Done with that business. I usually do repairs on everything myself, unless it's something really weird like this issue. I'm also not going to join yet another forum (hvac) so hopefully there's some experts here for my question.

I've got a Goodman GMV80704BXBA. A two stage gas furnace. I believe it's about 15ish years old.

I've had an odd intermittent error happen over the last few winters. In the past it eventually started working again.

The error it gives is solid red, which translates to "internal gv error, micro and frequency check". Searching the web turns up nothing.

What it has done previously:
- inducer comes in for varying amounts of time, maybe the igniter will ignite or maybe not. Most often not.
- solid red error.

What it's done this year:
- after a good amount of time with the power to it shut off, the first attempt the inducer comes on for 15s, then the igniter goes a short amount of time, maybe 5s, then goes to solid red error.
- when it retires, the inducer will shut off after a couple seconds and give a solid red error.

What I've concluded:
- pressure switches are good
- it's not the inducer controller board. I just replaced it today and it did the same thing even though an HVAC tech told me he was sure it was a bad board (I replaced the board about 5 years ago).
- it could be the transformer if there's a weird inconsistent 24v supply to the igniter, but probably not since the gas valve seems to work fine when it comes on.

Here's what happened today when troubleshooting after replacing the board and it still have the solid red error:
- I thought it had to be something with the igniter or gas valve due to the timing of it shutting down.
- unplugged the igniter and turned it on. It went through the whole 15s inducer pre purge and the 17s igniter warm up and opened the gas valve for a 4s flame sense. Tried it multiple times and it kept working.
- plugged the igniter back in and turn it on. It worked.
- turned it off, unplugged the gas valve wire harness and turned it on. It went through the whole cycle again without a hitch.

So here's a couple of questions:
- if there's something wrong with the igniter itself, can it throw that error even if it seems to come on the first time after being off awhile and then consistently throw the error after just 2s of pre purge?
- can the wire connection to the igniter do that?
- is there any kind of electrical check with the gas valve early in the inducer pre purge stage that would cause that error? It seems not likely since it went through the whole cycle and attempted to light even with the gas wire harness unplugged.


I am returning the new inducer PCB and going to get a new igniter and maybe a gas valve in case it quits working again.

 

[SwiftShot]

Sounds like a crazy problem to chase. I would think it could be the wire connection or the gas valve. Is it a 2 stage or single stage vavle. Ie does it run a pilot light as well? If so thermal couple could be giving false signal.

 

[HighUintas]

Sounds like a crazy problem to chase. I would think it could be the wire connection or the gas valve. Is it a 2 stage or single stage vavle. Ie does it run a pilot light as well? If so thermal couple could be giving false signal.

2 stage. No pilot light. It has a glow igniter. If the igniter has a bad connection or something wrong with it, I was thinking maybe the board monitors voltage in that circuit and throws an error if it's not in an expected range.

As far as I know, there is no electrical activity between the gas valve and board until the igniter hits the 17s warmup and the board tried to open.

 

[DenverCountryBoy]

Is the vacuum port on the inducer dirty/clogged? Is the tube to the pressure switch creating a good seal?

 

[ElkNut1]

Sounds like there's a possibility your flame sensor needs cleaned. Igniter works then gas ignites for 4 seconds & shuts off, that's generally a dirty flame sensor. Check it out on youtube.

ElkNut

 

[Weldor]

I had the same problem, changed board nothing. Hvac guy came out changed the inducer pressor switch and cleared the line. Worked for about a week. back to the same. Now it just takes 2-3 times to fire up. Had the gas company (propane) check pressure. 35 degrees seems ok, but at night it seems to either wick back or the tank freezes up? . Propane guy thinks at high pressure regulator at the tank to the house then low pressure at the house will solve the problem. Anyone heard of this. We're at 6000 ft. I will clean the flame sensor, never looked at that.

 

[ElkNut1]

Generally if you have ignition & the flame starts then it isn't the inducer/draft motor or pressure switch. When flame starts: the next sequence of events is for the flame sensor to register heat from the flame & send the message of OK to the control board, this tells the gas valve to continue producing gas to the already started flames. A dirty or sooted up flame sensor will not relay an OK message to the control panel thus shutting off the gas valve. A flame sensor is generally cleaned not replaced in most situations., Youtube will show you its location & how to clean it, it's a simple fix.

ElkNut

 

[HighUintas]

Is the vacuum port on the inducer dirty/clogged? Is the tube to the pressure switch creating a good seal?

No, the vacuum port and hose seals well and the pressure switches, both low and high work correctly. Other than being able to hear the switch, click on and off at the appropriate time and getting the correct voltage coming from the pressure switch at the appropriate time, it does not give me the error code for it losing pressure. I can pull the vacuum tube off the inducer, suck/release at the right time and it will give me the crusher switch error.

Sounds like there's a possibility your flame sensor needs cleaned. Igniter works then gas ignites for 4 seconds & shuts off, that's generally a dirty flame sensor. Check it out on youtube.

ElkNut

I have dealt with The flame sensor being dirty in this furnace once a year since I moved in, and that's usually the very first thing I do is clean the sensor. I cleaned it this year when I started troubleshooting it, so I Don't think it's that. Also, the fact that after the first try the inducer only runs for 2 seconds before erroring out, long before the igniter would even try to come on, leads me to believe it's not the flame sensor

 

[go_deep]

I had something similar years ago and it was the smart gas valve. Pilot light would light then turn off, the smart gas valve wasn't acknowledging the message that the pilot light ignited, so it shut gas off.

 

[ElkNut1]

Yes, so many things can be the culprit ! (grin) Do you have a water trap on your unit? If so make sure it's clear. Most have a shutoff to the panel if the trap or hoses get clogged or partially clogged. Also check the chimney system making sure there are no obstructions from the furnace to out the roof, it needs to draft properly or the unit will shut down. Just trying to help!

ElkNut

 

[HighUintas]

Yes, so many things can be the culprit ! (grin) Do you have a water trap on your unit? If so make sure it's clear. Most have a shutoff to the panel if the trap or hoses get clogged or partially clogged. Also check the chimney system making sure there are no obstructions from the furnace to out the roof, it needs to draft properly or the unit will shut down. Just trying to help!

ElkNut

Thanks for the ideas! Are you an HVAC tech? I've always wondered what the elknut does for his grown up job

Yes, there's a water trap. The drain PVC goes to a pump. I made sure that was clear.

I have not yet climbed up to look down the flue but will do that, maybe tonight. If there was a drafting issue up the flue, wouldn't that cause the pressure switches to disengage?

 

[ElkNut1]

You shouldn't have to clean your flame sensor once a year. You may need to adjust your flames at the gas valve. Your flames should be blue with little yellow showing. If you have dominant yellow flames then that will soot up your flame sensor prematurely. Seriously, I'd put in a new one for the 10.00 - 15.00 - Yours may be acting up but not out.

With proper flame adjustment you can go years without cleaning. Mine is going on 9 years without a single cleaning on natural gas.

No, not a licensed Hvac guy but I do a lot of repairs on them. (grin)

If it's only a partial obstruction then yes your ignition & flames will light but then it can shut down.

What's throwing me here is you have ignition & flames for 4 seconds then shuts down. that's generally a flame sensor issue. Maybe the control panel isn't reading the sensor?

ElkNut

 

[DenverCountryBoy]

If the igniter is not coming up to temp, either the pressure switch is not sending a signal or the igniter is bad or has a loose wire.

If any condensation made it into the pressure switch, that can cause the switch to rust and go bad.

I would try temporarily shorting the pressure switch to see if that is the problem. Don't leave it shorted though.

 

[ElkNut1]

OK, here's what a bit of research has shown on a solid red error code!

A solid red error code on a Goodman furnace typically indicates a safety lockout, meaning the furnace has detected a problem and has shut down to prevent damage; this could be due to a variety of issues like a faulty flame sensor, clogged gas valve, or a problem with the ignition system.

I'd look a bit further into the flame sensor as you've already addressed the other 2.

ElkNut

 

[HighUintas]

OK, here's what a bit of research has shown on a solid red error code!

A solid red error code on a Goodman furnace typically indicates a safety lockout, meaning the furnace has detected a problem and has shut down to prevent damage; this could be due to a variety of issues like a faulty flame sensor, clogged gas valve, or a problem with the ignition system.

I'd look a bit further into the flame sensor as you've already addressed the other 2.

ElkNut

Thanks! I didn't consider it being a lockout since it will continue to retry the inducer cycle (endlessly) but only works for a couple seconds after the first longer cycle errors and I thought the lockout prevents it from doing anything for awhile, but maybe that isn't the case.

I'll get another flame sensor to try in case it quits working again.

If you're correct it is a lockout after detecting an issue with ignition, it's possible it could be a gas valve blockage. For whatever reason, there's no drip leg in the nat gas inlet before the valve. The supply pipe comes down vertically, then splits to the water heater (has drip leg before valve because I installed it) and then an elbow to the flexible gas line. Flexible gas line loops upward to a straight iron gas pipe (12-16") into the valve. I thought it wasn't the valve because it started working after unplugging the igniter.... Perhaps it was just a coincidence and the blockage or whatever it is in the gas valve fixed itself at the same time I unplugged the igniter.

What fun!!

 

[ElkNut1]

Ha Ha, you got that right about the fun! (grin)

A lockout means it has retried too many times without the issue resolved thus nothing working as it should.

Replace the flame sensor then shut off all power to the furnace for a minute or so then restore power, it should reset itself. Fingers crossed!!!!

ElkNut

 

[ElkNut1]

Make sure your filter is in good shape too. most should be changed every 3 months.

ElkNut