Furnace intermittent problems

[OverkillYJ]

So I had a furnace that stopped working last year. This year I opened the cover, blew it out with air, and turned it on and it worked for a few days. Its a high efficiency Ruud forced air gas furnace. Now it stopped working again.

It is going through the start sequence, and the ignitor is glowing red, but I am getting no ignition. I do not smell gas, and I also took a torch to see if an open flame would light the burners, and I am getting nothing. Seems I have no gas flow.

Does this mean the gas valve is broken? Are those universal? Can I just get another, or is it going to be a pain? The furnace is 30ish years old and hanging from the inside of my shop roof. I would like to repair it in place if possible.

Thanks for any help you can offer. I included a pic of the label in case anyone can tell me anything specific about this problem.

 

[Jim greengo]

Is there gas getting to it?

 

[nadogail]

Have you checked that gas is getting to the valve, and that the pilot valve is being energized?

 

[41ratrod]

our was doing that off and on I taped on the gas valve with a small wrench and it would work for a few days last week I pulled the two wires off to check the contacts and put the wires back on. now it's ok. I HOPE

 

[OverkillYJ]

So yes, it has gas. This furnace uses an electric ignitor. After I posted I messed with it some more, then it worked for a few hours, now it stopped again.

Does a replacement gas valve need to be exact? The manufacture date on this is 88. I will just fix everything that breaks if there are universal parts. The furnace would be very difficult to replace in the location its in.

 

[danski0224]

Odds are, if it worked and then stopped, the problem is something else.

It really should be looked at by someone that has a combustion analyzer and that presumably knows how to use it. This (in addition to some other things) can determine if the furnace is actually safe to use. Like it or not, there is a finite lifespan to these things if the problem isn't a minor one.

There is a real danger in just continuing to throw parts at it while using random snippets of information from the internet.

There is a possibility that an equipment safety IS functioning properly and is preventing a bigger problem, which can include death from CO poisoning.

Accessibility for service or replacement (or none of those) is something that should be considered when equipment is put into service...

Good luck.

 

[OverkillYJ]

Odds are, if it worked and then stopped, the problem is something else.

It really should be looked at by someone that has a combustion analyzer and that presumably knows how to use it. This (in addition to some other things) can determine if the furnace is actually safe to use. Like it or not, there is a finite lifespan to these things if the problem isn't a minor one.

There is a real danger in just continuing to throw parts at it while using random snippets of information from the internet.

There is a possibility that an equipment safety IS functioning properly and is preventing a bigger problem, which can include death from CO poisoning.

Accessibility for service or replacement (or none of those) is something that should be considered when equipment is put into service...

Good luck.

OK Captain Obvious.

The furnace has a Kiddie CO meter on the side of it with an alarm and fresh batteries.

The furnace is in a shop roof, which is a normal place to have a furnace in a commercial shop, and many other commercial buildings.

The Solenoid in the gas valve tested bad, so I ordered a new gas valve.

The furnace is going through the ignition sequence so everything in it is testing good and the ignitor is glowing. Its not getting fuel.

NOS gas valve was $35 and is on the way.

 

[bonneyman]

Was the bad gas valve a Robertshaw brand? Rectangular and relatively thin valve? Those had diodes built into the valve which took the 24v AC signal from the t-stat and converted it to 12v DC as the valve was DC. Robertshaw's attempt at cutting costs back then. A diode goes bad, you get intermittent operation.

Just curious.

 

[gmcgeo]

OK Captain Obvious.

The furnace has a Kiddie CO meter on the side of it with an alarm and fresh batteries.

The furnace is in a shop roof, which is a normal place to have a furnace in a commercial shop, and many other commercial buildings.

The Solenoid in the gas valve tested bad, so I ordered a new gas valve.

The furnace is going through the ignition sequence so everything in it is testing good and the ignitor is glowing. Its not getting fuel.

NOS gas valve was $35 and is on the way

Nice, i was going to suggest the gas valve giving you issues. \

sometimes "depends on the gas valve" the magnet wont drop opening the valve. And in your case the solenoid is not operating correctly. and other times no power is going to the solenoid. glad you found the issue, that's half the battle sometimes

 

[OverkillYJ]

Was the bad gas valve a Robertshaw brand? Rectangular and relatively thin valve? Those had diodes built into the valve which took the 24v AC signal from the t-stat and converted it to 12v DC as the valve was DC. Robertshaw's attempt at cutting costs back then. A diode goes bad, you get intermittent operation.

Just curious.

Yes it is. You are correct.

 

[Jackfre]

Thanks, Capt Dankski, for stating the obvious!

 

[danski0224]

Thanks, Capt Dankski, for stating the obvious!

Glad to help.

All kidding aside, as someone that has condemned equipment with a combustion analyzer that otherwise appeared to be "functioning properly", I am always in favor of having equipment checked out professionally.

That said...

I have also seen equipment that has been condemned that is functional and safe, but the company/"technician" was looking to make a scare tactic sale. Never, ever has the customer seen pictures of the flaw or a combustion analysis report.

These scare tactic pressure sales tactics give the HVAC industry a bad rap. I live in an area where no State licensing is required to be an HVAC contractor.

It is also an industry where the customer gravitates to the lowest bid or "service special of the week". Or internet forums for sometimes questionable advice.

The customer almost never understands the importance of the system that uses approximately 50% or more of their energy dollars.

I certainly hope that the OP does get the equipment checked out, even if the part appears to have fixed the issue.

 

[bonneyman]

Yes it is. You are correct.

Cool!

When you replace the valve, take the old valve and pop the black plastic cap off that is around the screw terminals. There should be 2 or 3 diodes and a mini-circuit board under there. See if any of the diodes look darkened and burned. Turning the voltage from 24v AC to 12v DC means 12 volts is going to have to go somewhere. It turns into heat. The body of the valve acts a little like a heat sink but the diodes get stressed and eventually fail.

 

[OverkillYJ]

Cool!

When you replace the valve, take the old valve and pop the black plastic cap off that is around the screw terminals. There should be 2 or 3 diodes and a mini-circuit board under there. See if any of the diodes look darkened and burned. Turning the voltage from 24v AC to 12v DC means 12 volts is going to have to go somewhere. It turns into heat. The body of the valve acts a little like a heat sink but the diodes get stressed and eventually fail.

So I got the new valve today. Furnace fired right up.

I took the black plastic cap off and saw the diodes, but none were bulging or blatantly burned up, which surprised me.

I did notice this though. When I put the new fuel valve in and turned the furnace on, the sound of the gas valve opening was much louder and stronger sounding on this new used valve I got. I also have stronger flames. So I am guessing corrosion inside somewhere stopped the valve from opening internally all the way until it completely failed, but I dont know for sure.

 

[danski0224]

Can also be from missing or improperly installed dirt leg on the gas pipe.