# Comfortmaker furnace won't fire



## Scott Little (Sep 7, 2010)

I have an 8 year old Comfortmaker sealed combustion furnace. The A/C works fine, however, the furnace won't fire. It does not start the firing sequence while in heating mode. I've checked the thermostat and it is fine and switches in heating mode, however, the furnace does not attempt to fire. Does this sound like a control board issue, or are there potentially safety switches that are preventing this from firing? It has had annual maintenance through 2008, however missed it lat year.


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## Marty S. (Oct 31, 2009)

Scott, you'll need a meter to check voltages. Should be 24 volts between C and W on the furnace control board if it's getting a call for heat from the thermostat. From there the control board should send 120 volts to the inducer motor. If you have both of those but the motor doesn't spin take the flue pipe off and look for a dead bird or squirrel jammed in the inducer wheel.


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## Scott Little (Sep 7, 2010)

*voltage good, no dead animals*

Thanks for the reply. I applied 120 directly to the inducer and it sounded like there was a lot of water in the housing. I pulled it out, drained it and asked my 4 year old son if he sprayed water down the white pipe outside. He said he did it last week. Anyway, got the system dried out. Wasn't expecting that little twist...back to the issue at hand. I inspected everything and fired the inducer motor up again via extension chord and checked to make sure that both intake and exhaust were clear and working fine...not problem there...lots of flow and the inducer motor sounds fine. I obviously had a plugged drain and disconnected and cleaned all drain lines.

I disconnected all switches and jumped them out. 

Result...no worky.

Voltage from the C to the W on the control board is low...almost zero with the thermostat calling for heat...set to 90 degrees F.

I tested the transformer that powers the control board and it is putting out 25.6 VAC...so that is not the problem. 

I crossed the C to Y on the control board and the air fired, however, when I cross the C to W on the control board, nothing happens. That is really the only reason I haven't checked continuity on the white wire, and also because all connections look fine and we haven't had any major structural issues or anything happen that could have disrupted the thermostat wiring.

I am ready to order a new control board...do you agree, or do you think I may have missed something?

Thanks again for your help.


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## yuri (Nov 29, 2008)

Take all the wires off the terminal strip and label them. Then put a jumper between R and W. That simulates a call for heat. Ventor fan should start running etc etc. If that works then you have a bad tstat or faulty wiring to/from it. Check if there are any error codes flashing on the gas valve or circuit board when trying to call for heat with that jumper on. Should be a legend of them on the back of one of the doors and in the manual.

Post the model# and pics of it. Lots of variations of that furnace out there.


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## hvaclover (Oct 2, 2008)

yuri said:


> Take all the wires off the terminal strip and label them. Then put a jumper between R and W. That simulates a call for heat. Ventor fan should start running etc etc. If that works then you have a bad tstat or faulty wiring to/from it. Check if there are any error codes flashing on the gas valve or circuit board when trying to call for heat with that jumper on. Should be a legend of them on the back of one of the doors and in the manual.
> 
> Post the model# and pics of it. Lots of variations of that furnace out there.



C to W ?!

Yuri direct short...blown fuse or the board got damaged by the water...


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## yuri (Nov 29, 2008)

Anything is possible when "jumpering" is involved.:whistling2:

Betcha it has the new "improved" idiot valve.


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## kenmac (Feb 26, 2009)

hvaclover said:


> C to W ?!


 
About time you caught that:laughing:


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## Scott Little (Sep 7, 2010)

Let's clear up a point where I mis-spoke...I jumped red to white at the board and got no repsonse, not C to W. I did check the voltage between C and W however, and there was none. When I connected red to yellow, cooling turned on. The induction motor seems to have survived the water...no birds.

The light on the Honeywell gas valve is a constant green. There are no lights or indicators on the control board.

The control board shows no signs as to ever having been wet and the fuse is intact. 

The heating cycle does not kick in at all, the inducer motor does not start unless I supply power independently.

I will disconnect the wires as you mentioned and jump R to W again in the morning.

I had a spare stat from a former house and tried that with the same results.

Also, will get the model of the furnace.

Thanks again for your continued assistance.


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## hvaclover (Oct 2, 2008)

kenmac said:


> About time you caught that:laughing:


 
What was my time coach?????????


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## hvaclover (Oct 2, 2008)

Scott Little said:


> Let's clear up a point where I mis-spoke...I jumped red to white at the board and got no repsonse, not C to W. I did check the voltage between C and W however, and there was none. When I connected red to yellow, cooling turned on. The induction motor seems to have survived the water...no birds.
> 
> The light on the Honeywell gas valve is a constant green. There are no lights or indicators on the control board.
> 
> ...


 You have a bad Smart valve.


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## Scott Little (Sep 7, 2010)

I am not arguing the poetential for a problem with the smart valve, however, after looking it up (Honeywell SV9541) I found there were no error codes indicating any malfunction. Therefore the only potential is that a triac in the smart valve is smoked or the control board is done. The fact that the system turns on and works properly in cooling mode supports your theory that the smart valve has malfunctioned. Would it not, however, give some kind of error message if it failed internally?

BTW...I checked continuity on the White wire and the wire is sound.

Sorry to keep dragging this out...it looks like we're down to control board or valve. 

Thanks to everyone for pitching in! Give me your votes and I will get on with ordering parts for the repair.

Comfortmaker - N9MP2075B12A2
Honeywell - SV9541
Control Board - ST9160B 1050

Thanks!


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## hvaclover (Oct 2, 2008)

Scott Little said:


> I am not arguing the poetential for a problem with the smart valve, however, after looking it up (Honeywell SV9541) I found there were no error codes indicating any malfunction. Therefore the only potential is that a triac in the smart valve is smoked or the control board is done. The fact that the system turns on and works properly in cooling mode supports your theory that the smart valve has malfunctioned. Would it not, however, give some kind of error message if it failed internally?
> 
> BTW...I checked continuity on the White wire and the wire is sound.
> 
> ...


The valve controls inducer and ignition operation. The board controls only the blower for ac and heat cycles.

The valve has 24 volt and 110 volts supplying it. These valves are known for their frequency of break down and unpredictable false codes.

The voltages are/ will read unusual values.

You should have a dim-bright-dim-bright rhythm when normal.

You have a continuous 'ON" fault light. That is not even listed in the fault code directory.(as stated above Smart valve's notorious reputation for misleading fault codes)

In short your Smart Valve has become retarded. Time to replace it.

Warning: Be prepared for valve sticker price shock.

http://customer.honeywell.com/techlit/pdf/PackedLit/69-1227.pdf


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## yuri (Nov 29, 2008)

Snoop thru here and you may be able to find a troubleshooting manual. Those furnaces are a huge pain in the azz to troubleshoot.http://gocomfortmaker.com/go/index.asp


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## hvaclover (Oct 2, 2008)

yuri said:


> Snoop thru here and you may be able to find a troubleshooting manual. Those furnaces are a huge pain in the azz to troubleshoot.http://gocomfortmaker.com/go/index.asp


 Ain't nothing in there to trouble shoot. That's what the honey link I provided was for.

There is not even a fault code chart in the those spec manuals on the site.

I do Heil and did alot of those stupid valves that are dual voltage. The OPs description of the problem is typical for this furnace and even Lennox Armstrong concord furnace line has a high failure rate with that valve. And the fault codes in most cases don't give a true story of what the problem is.
Of course even on systems with accurate fault codes, they are used only as a reference and the tech will use his experience and accurate test reading to discover the truce cause of failure.

I had one recently that kept flashing a closed press switch before ignition.
I worked around the the false code and discovered it was the valve dropping out the ignition so quickly it fooled it self into a false flash code.


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## yuri (Nov 29, 2008)

I do 80% Lennox and 20% of the other brands. Don't run into many of them and never liked them when I did. Just have to slog thru them when I do. Very little Armstrong stuff up here.


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## hvaclover (Oct 2, 2008)

yuri said:


> I do 80% Lennox and 20% of the other brands. Don't run into many of them and never liked them when I did. Just have to slog thru them when I do. Very little Armstrong stuff up here.


 Did you ever try to measure low voltage on one that works?

You picked the right word< SLOG>. You waste time checking the fault code only to find some thing else wrong.

That's why ICP changed from smart vales to standard 24v reundant valves. Concord gave up on them too.


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## yuri (Nov 29, 2008)

Yah, they also have some 13 or 18 volt readings on some of those idiot valve systems. You need to check to C and not ground, yada yada yada. Then there was that bizarre home grown ECM motor that they concocted and no else heard of and now requires a retrofit. I prefer my brand.:thumbup:


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## hvaclover (Oct 2, 2008)

yuri said:


> Yah, they also have some 13 or 18 volt readings on some of those idiot valve systems. You need to check to C and not ground, yada yada yada. Then there was that bizarre home grown ECM motor that they concocted and no else heard of and now requires a retrofit. I prefer my brand.:thumbup:


 LOL I wanted to mention how whippy the low voltage reading but I didn't think anybody would take me serious.

The xfmr common is a thing stricly unique to Lenoox. They, Lennox are wound in such a way that you can only measure measur 24V at the secondary side of the xfmr itself.

Used to drive me nuts til I went to some RSES classes.


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## kenmac (Feb 26, 2009)

I would like to meet the idiot that named it smart valve. Wonder if he's as smart the valve he invented ?


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## hvaclover (Oct 2, 2008)

kenmac said:


> I would like to meet the idiot that named it smart valve. Wonder if he's as smart the valve he invented ?


He's in a Mexican land fill surounded by hundredsof his brillant (but dead)valves.


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## Scott Little (Sep 7, 2010)

*Thank you everyone!*

Thanks for your help everyone!

I'll get the valve...still dealing with the sticker shock.

The voltage on the cooling cycle was a few tenths shy of 24 as I recall. 

I truly appreciate all of your help!

Scott


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## hvaclover (Oct 2, 2008)

Scott Little said:


> Thanks for your help everyone!
> 
> I'll get the valve...still dealing with the sticker shock.
> 
> ...


 Enroll the old valve is special ed clases. You might be able to reabilitate it:whistling2:


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## Ryky112 (Sep 10, 2010)

*Cart before the horse?*

I wouldn't go changing expensive parts until you've exhausted all other options. I don't know that brand of furnace that well but most newer furnaces have air proving switches. They are usually round and have tubing going to the inducer housing. Take the tube off the inducer housing and clean it out with a sewing needle. 
See if that works for ya.


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## Ryky112 (Sep 10, 2010)

Oops... Just re-read the thread... seems I didn't catch the fact that your inducer motor wasn't coming on at all... please disregard my last post... I'll read more carefully next time
Sorry


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## hvaclover (Oct 2, 2008)

Ryky112 said:


> Oops... Just re-read the thread... seems I didn't catch the fact that your inducer motor wasn't coming on at all... please disregard my last post... I'll read more carefully next time
> Sorry


Been partying with Newfies, eh?



Attached Images


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## Scott Little (Sep 7, 2010)

*Valve works but pilot light does not always work*

Thanks everyone for their help. I thought I had the situation under control. I replaced the smart valve. The valve light goes bright then dims as it is supposed to. The pilot did not light the first try...I suspect that there was too much air in the gas train. It did ignite and fired properly on the second try. 

Problem solved...I thought...2 days later when I went to fire up the furnace and adjust the gas pressure if needed, the pilot would not light. No manual shipped with Smart Valve and the pilot adjustments in the manual I found on line do not exist on the smart valve I purchased, nor did they on the one I replaced. Their is a phillips head screw on the smart valve next to the tubing that feeds the pilot. Is that a pilot adjustment?

Do you think it is a simply adjustment at this point? The smart valve is not indicating any issue. The inducer runs, the hot ignition glows red, I just don't get gas out of the smart valve and don't understand why.

Thanks again,

Scott


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## Scott Little (Sep 7, 2010)

*Got It!*

So...I found the pilot adjustment and then set the gas pressure with a manometer.

Thanks everyone for the help.

Total cost $250 for valve and shipping.

You guys helped me save at lease that much!:thumbsup:


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