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+--- Thread: PAGING FURNACE REPAIRPESON (/showthread.php?tid=88672)
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PAGING FURNACE REPAIRPESON - Black - 11-30-2009
We actually don't seem to have too many of those around theses parts, but who knows . . .
Had a furnace that hadn't been putting out heat since the spring-- replaced the flame sensor and now it kicks in consistently after the second try, i.e. the igniter glows the first time but then gives up, and then the second time around it apparently gets the heat close enough to the sensor to open the gas valve.
Is this the way it should be?
The original sensor was one of these:
http://www.appleapplianceparts.com/b1172606-janitrolgoodman-gas-furnace-flame.html
And the replacement is one of these:
Thx!
Re: PAGING FURNACE REPAIRPESON - Forrest - 11-30-2009
First off, I'm not a furnace repairman. I'm just a home owner with a gas furnace with the same problem. The owner's manual for my Payne furnace states if the heat sensor isn't working properly, clean the sensor with steel wool. I now clean the sensor once or twice a year and my furnace works fine.
Re: PAGING FURNACE REPAIRPESON - Black - 11-30-2009
Thanks-- tried cleaning the original but it didn't help.
Anyways, I wasn't looking for a repairman, I was looking for a repair peson :-)
Re: PAGING FURNACE REPAIRPESON - deckeda - 11-30-2009
I once had a weak igniter. It lit, but poorly, or seldom, and there was the smell of unburned gas when the furnace ran (which is why we called for a repairperson.)
Just wondering if your igniter isn't fully up to snuff. Didn't watch all the steps he took but it seemed like a really simple swap. Part was less than $100.
Re: PAGING FURNACE REPAIRPESON - M>B> - 11-30-2009
The part in the image is called a thermocouple.
Re: PAGING FURNACE REPAIRPESON - Black - 11-30-2009
deckeda wrote:
I once had a weak igniter. It lit, but poorly, or seldom, and there was the smell of unburned gas when the furnace ran (which is why we called for a repairperson.)
Just wondering if your igniter isn't fully up to snuff. Didn't watch all the steps he took but it seemed like a really simple swap. Part was less than $100.
I guess my igniter is like the one on this page:
http://americanhvacparts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BURN252603&Category_Code=Bgoo
It's all the way to the right while the flame sensor is all the way to the left. I think the igniter only does its thing at the moment the gas valve opens, and the gas valve doesn't open until the flame sensor tells it it senses heat; I think there's some sort of a long thing that glows first.
Need some edumicatin' . . .
Or maybe the igniter transfers its heat into some other metal part (it sure looks like the glow spreads all the way across)-- reminds me of my coleman stove a bit-- doesn't burn well until the metal fins are all heated thoroughly. You can see the glow spreads a little farther due to the preheating effect the second time around, which is then enough to trip the gas valve.
Re: PAGING FURNACE REPAIRPESON - Black - 11-30-2009
M>B> wrote:
The part in the image is called a thermocouple.
Yeah, thanks, mine is called a flame sensor-- there's no thermocouple in this unit.
Re: PAGING FURNACE REPAIRPESON - Black - 11-30-2009
Found this-- by far the most (and possibly only) knowledgeable forum post out there:
Therinnaiguy
Rank: Guru Air Conditioners Expert
Rating: 88%, 412 votes
On a call for heat, the 24 volt thermostat sends a signal to the control module. The control module will indicate a call for heat with a light on the control either blinking or remain solid depending upon model. The inducer (exhaust) blower will purge all gasses from the furnace and pressurize a pressure switch. Once the pressure switch tells the module to continue, the electronic ignition will energize and send 120 volts to the igniter. The igniter will glow and you will be able to see it if viewed thru the small inspection port. Once the igniter gets hot enough, it sends a signal to the module opening up the gas valve (24 volts). Either a pilot will come on or the burner tube will ignite then spread the flame to all burners. Lastly a safety sensor will be looking for a certain temperature within a few seconds and the furnace will continue to operate and the room air blower will turn on in a minute or two.
What could go wrong? The unit will not run if there is no signal from the thermostat (bad thermostat or broken wire), the control module does not sense a signal from the thermostat (bad control), the inducer does not energize (bad motor), the pressure switch does not close (blocked vent piping, bad switch, plugged condensate hose), the igniter does not energize (bad control, bad igniter), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not light (dirty pilot), the burner does not light (bad burner, plugged orifice, not enough combustion air), the flame does not spread to each burner (bad flame spreader, dirty flame spreader, more bad burners), the flame safety sensor does not detect flame (dirty or bad flame spreader, bad flame sensor, broken wire, bad control), or the room air blower does not energize (bad fan motor, bad control).
A friend who used to do hvac mentioned the vacuum hose. Meant to take a look at it tonight when I was back over there but forgot. According to this info, the flame sensor is only a failsafe to make sure it's working once it's fired up and to kill the gas if not. My problem seems to be happening before this; the igniter glows much hotter the second try . . .
Also looked through my pics-- sad when you can only read something by getting a photo of it and looking at that later; the furnace is a Goodman GMP 100-3 Rev. A.
Re: PAGING FURNACE REPAIRPESON - macphanatic - 11-30-2009
The flame sensor is a thermocouple. It senses flame by the heat generated. Industrial equipment sometimes uses optical flame sensors in conjunction or lieu of thermocouples.
Re: PAGING FURNACE REPAIRPESON - Black - 11-30-2009
macphanatic wrote:OK, thanks.
The flame sensor is a thermocouple. It senses flame by the heat generated. Industrial equipment sometimes uses optical flame sensors in conjunction or lieu of thermocouples.
My question was whether it's normal/OK for the furnace to flame up on second igniter glow rather than first.