furnace problem

drunkenmaxx · Post by **drunkenmaxx** » Tue Dec 04, 2007 10:03 pm

ok, i have a gas furnace with automatic ignition. (no pilot) this morning when we got up, it was really cold in the house. we checked the thermostat, it was reading 58, we had it set to 67. so, the furnace isn't kicking on. can anyone offer some trouble shooting before i bend over for a repair guy to ram me?

Whelan · Post by **Whelan** » Tue Dec 04, 2007 10:20 pm

Let me ask my buddy for some insight, cause it could be a number of problems. He owns his own Heating & Cooling business Could be any of the following though:1) broken thermostat2) faulty switch on the panel for the furnace3) safety on the furnace that won't let it turn on due to it needing service or cleaning

Sublimewind · Post by **Sublimewind** » Tue Dec 04, 2007 10:34 pm

My dad is an HVAC guy and he would say it's either the thermocouple which is basicly a tempature dependant switch that lets the furnas know it's lit.... When it goes bad, the "computer" thinks the furnas isn't lighting and shuts down for safety... Thinking that it will fill the house with gas.... The second thing would be the main board is bad, which is like a 100$ fix. Both of which you will prolly have to call the repair guy to take care of... The thermocouple is an easy one, you "could" do yourself, it looks like a long copper tube that screws into the main control board and into the main body of the heater element... and again is usually coiled up at one point or another... The main board has trouble shooting tests that can be done, but unless you are well versed with it, and a DMM, it's going to be difficult to explain.... Good luck, get something done soon, there is no telling how long it might take to get the proper main board if that's the problem... also, find the name of the unit, and try to talk to places fimillar with that brand, if you can... they are all basicly the same, but different at the same time... EDIT: something else you could look at, you might have to remove a cover or 2 to find the main board, but there "could" be a board mounted fuse that might have blown...

millster · Post by **millster** » Tue Dec 04, 2007 10:36 pm

I just repaired my furnace about a month ago with the same problem. A couple of questions I have...1)Do you have a digital thermostat? If so, does it show that the thermostat is calling for heat? Mine was and the furnace would actually start to run and then stop.2)Does the central control box inside your furnace have a diagnostic light? In many cases, there will be a small light on the box that will flash to indicate particular failures. A couple of things to check, though... make sure both access panels on the front of the furnace are on tight. Sometimes they won't run if one is loose.If you have a digital thermostat, try resetting it. Pull it off the wall and remove the batteries. Let it sit for a few seconds and then put it all back. I've also had the wires on the thermostat back out over time due to vibration or heat or something. That house was a bit quirky anyway, though.Mine just ended up being a small vacuum switch that runs between the back of the exhaust blower and the top of the exhaust flue. I have no idea what its purpose is, but that's what the diagnostic light indicated was wrong and it's what I replaced. So far, so good.

drunkenmaxx · Post by **drunkenmaxx** » Tue Dec 04, 2007 10:40 pm

thanks for the replies everyone.yes millster, i have a digital thermo and it's switched to the proper position. i did notice a green flashing light inside the panel of the furnace. (i saw it through the vents)

millster · Post by **millster** » Tue Dec 04, 2007 10:42 pm

Does your thermostat tell you if the system is actually active though? Mine will say "Heat On" when the furnace is (or should be) running.Take a look at the front of the main board box in the furnace. It should have a key for what the flash patterns mean. For me, it was a lifesaver. Meant spending $40 to replace a switch rather than $200 for a service call. Actually, this wouldn't by chance be a Coleman, would it?

Whelan · Post by **Whelan** » Tue Dec 04, 2007 10:43 pm

Sub's apparently got this one on lockdown lol.I usually just give my buddy a call then take him out for some "let's get smashed" time at the bar. Actually, tonight may be a lets get smashed night.

drunkenmaxx · Post by **drunkenmaxx** » Tue Dec 04, 2007 10:44 pm

i'm sorry whelan, but what the hell are you talking about?i'm not sure what kind of heater it is millster, i'm not home so i can't look. where do you purchase such parts? at hardware store?

Sublimewind · Post by **Sublimewind** » Tue Dec 04, 2007 10:49 pm

Quote, originally posted by drunkenmaxx Â»thanks for the replies everyone.yes millster, i have a digital thermo and it's switched to the proper position. i did notice a green flashing light inside the panel of the furnace. (i saw it through the vents)My day (again a former HVAC guy) does NOT like the digital thermostats at all, they are much more "prone" to failure than the good'ole dial types...I think Millster is on to something, lest hope it's what works for ya...

millster · Post by **millster** » Tue Dec 04, 2007 10:51 pm

I actually ended up calling an HVAC repair shop (one that specializes in my brand) and just telling them what part I needed. They sold it to me without hesitation. It seems when you come across knowing what you need they don't question you.

Sublimewind · Post by **Sublimewind** » Tue Dec 04, 2007 10:54 pm

Quote, originally posted by millster Â»I actually ended up calling an HVAC repair shop (one that specializes in my brand) and just telling them what part I needed. They sold it to me without hesitation. It seems when you come across knowing what you need they don't question you.Yep, that's how it works most times, that or they're waiting for a call later, you begging them to come out to fix the mess you just maid...

Whelan · Post by **Whelan** » Tue Dec 04, 2007 11:00 pm

Cause my friend owns his own HVAC company, so I get the work done for free.We tried using the digital thermo's with the programmable settings for temps and such. Never worked right so we now stick to the dial, never failed us yet.

drunkenmaxx · Post by **drunkenmaxx** » Tue Dec 04, 2007 11:01 pm

Quote, originally posted by Sublimewind Â»My dad (again a former HVAC guy) does NOT like the digital thermostats at all, they are much more "prone" to failure than the good'ole dial types...I think Millster is on to something, lest hope it's what works for ya... after millster's comments and some googling, it appears that something in the furnace itself is erroring out. i read that it may be as simple as over heating due to dirty air filter. (very possible, not changed in over a year!)

BlueCrush · Post by **BlueCrush** » Tue Dec 04, 2007 11:09 pm

Mine had the same problem as Millster's a couple years ago. Had to have somone comeout and replace the main circuit board. No filter change for a year?? wth! That may be contributing to your problem. It might be sensing that there is not adeuate air flow so it is shutting down or not starting up.

drunkenmaxx · Post by **drunkenmaxx** » Tue Dec 04, 2007 11:14 pm

i know i know, being lazy/forgetful can really screw some stuff up.

Whelan · Post by **Whelan** » Tue Dec 04, 2007 11:20 pm

Wow! We change our filter twice a year, once when it goes to A/C and again when it goes to heat.

blue_can · Post by **blue_can** » Tue Dec 04, 2007 11:48 pm

You only find a thermocouple in appliances with a pilot light - it is way of keeping the gas valve open for the pilot. For the main flame there is a flame sensor which uses flame rectification for flame sensing (at least on most modern furnaces).Have you opened the furnace and watched the ignition sequence. Is it spark or hot surface ignition. If it is hot surface you should be seeing the ignitor glow orange. Does the vent motor run. If it locks out before getting to ignition it could be the vent motor or pressure switch. If it gets to ignition stage but the ignitor does not light it could be a faulty ignitor. If it lights and then goes out you could have a dirty flame sensor or the overheat stat is causing a lockout. You could try cleaning the flame sensor with some steel wool.It could also be the thermostat.Just a few ideas for you to check. The service manual may have a troubleshooting guide which should help you figure this out.Furnace repairs are not difficult and although I have re-piped a furnace down to the gas valve normally I recommend leaving this to pros for most people unless you have the correct equipment.

blue_can · Post by **blue_can** » Tue Dec 04, 2007 11:54 pm

Quote, originally posted by blue_can Â»Mine just ended up being a small vacuum switch that runs between the back of the exhaust blower and the top of the exhaust flue. I have no idea what its purpose is, but that's what the diagnostic light indicated was wrong and it's what I replaced. So far, so good.That's to tell the furnace controller that the vent motor is running. If not the furnace should not be lit as there is no draft induction and the combustion gases will not be exhausted as this is a vented system.

Sublimewind · Post by **Sublimewind** » Wed Dec 05, 2007 12:14 am

Sweet, we gotta HVAC guy in da housssse

blue_can · Post by **blue_can** » Wed Dec 05, 2007 2:28 am

LOL..I'm not an HVAC guy at all. At least I don't do that for a living.

Sublimewind · Post by **Sublimewind** » Wed Dec 05, 2007 2:41 am

Quote, originally posted by blue_can Â»LOL..I'm not an HVAC guy at all. At least I don't do that for a living.Are you sure?? You sound a lot like my dad when he geting back into his HVAC stuff... (retired)

blue_can · Post by **blue_can** » Wed Dec 05, 2007 2:46 am

Yeah pretty sure. I'm an electrical engineer and work in R&D developing integrated circuits for things like wireless, audio, video, satellite and that kind of stuff.I'm quite a serious DIYer though.

drunkenmaxx · Post by **drunkenmaxx** » Wed Dec 05, 2007 3:09 am

well, first of all, thanks to everyone with advice!second of all, i'm home and got it working! i just reset it by turning the power off and turning off the gas for five minutes. (per instructions on the removable door.) i am going to replace the filter after the house warms up, i am pretty sure that is what caused it to shut off in the first place. (poor flow can apparently cause the unit to overheat)

BlueCrush · Post by **BlueCrush** » Wed Dec 05, 2007 3:32 am

Quote, originally posted by drunkenmaxx Â»well, first of all, thanks to everyone with advice!second of all, i'm home and got it working! i just reset it by turning the power off and turning off the gas for five minutes. (per instructions on the removable door.) i am going to replace the filter after the house warms up, i am pretty sure that is what caused it to shut off in the first place. (poor flow can apparently cause the unit to overheat)Good to hear, Drunken. Glad you got it working.

Sublimewind · Post by **Sublimewind** » Wed Dec 05, 2007 3:41 am

Quote, originally posted by drunkenmaxx Â»well, first of all, thanks to everyone with advice!second of all, i'm home and got it working! i just reset it by turning the power off and turning off the gas for five minutes. (per instructions on the removable door.) i am going to replace the filter after the house warms up, i am pretty sure that is what caused it to shut off in the first place. (poor flow can apparently cause the unit to overheat)Sweet, nothing worse than forzen and possibly broken pipes..!!

drunkenmaxx · Post by **drunkenmaxx** » Wed Dec 05, 2007 4:00 am

got the new filter in and she's purring like a kitten! total repair cost: $1.99 + tax

blue_can · Post by **blue_can** » Wed Dec 05, 2007 5:10 am

Good to hear it was nothing serious. Yes, a clogged filter can cause an overheat condition. Recycling power or resetting the overheat stat should fix that. Also it is possible the controller got hung up â€“ power cycling should reset that.Things I do to keep the furnace in good running order.1.Frequently change the filter. I have allergies so I use the more expensive filters. They do clog up more easily. Also I installed a climate control system along with a whole house humidifier a while ago and that has a â€œre-circulateâ€ function which is nice but also requires a filter change sooner. I typically change the filter about 3 times a year.Other things I do every year.1.Open up the furnace and clean the blower fan vanes.2.Remove the vent and clean it out with a vent brush.3.Blow compressed air through the burners to clean out dust and dirt accumulations4.Clean flame sensor with steel wool.5.Light up and make sure the flame is deep blue with occasional orange flecks.6.check for gas leaks with my electronic gas detector (too lazy to do it this year). You can check for CO leaks from the vent with that also but Iâ€™ve not checked that in w while.I also have a CO detector in the house.

blake31 · Post by **blake31** » Wed Dec 05, 2007 12:12 pm

Quote, originally posted by blue_can Â»4.Clean flame sensor with steel wool.my furnace was acting up a couple years ago, and this was my problem. now if anyone tells me their furnace is acting up the same way, this is the first thing i tell them to do. i cleaned my sensor with sandpaper, and it was back up running. easy thing to do before you call out a repairman.

kevera · Post by **kevera** » Wed Dec 05, 2007 12:20 pm

Quote, originally posted by blue_can Â» flame sensorMy hot water tank chews these up,about once a year.

blue_can · Post by **blue_can** » Wed Dec 05, 2007 1:11 pm

Quote, originally posted by kevera Â»My hot water tank chews these up,about once a year. I guess you mean thermocouple. The thermocouple provides a fixed voltage to keep the pilot light's gas valve open while the flame sensor in a boiler/furnace uses flame rectification to sense flame.Not sure why you would go through them like that.I went tankless about 4 years ago (installed it myself of course ) and I quite like it. The burner is sealed so they do not require flame sensor cleaning. So far have not had any problems with it.

Mario · Post by **Mario** » Wed Dec 05, 2007 7:58 pm

Aw, I missed out on this one. Didn't even get to show off...Get your furnace services one a year, regular maintenance will save you in the long run (just like a car). Unmaintained gas fired appliances can be dangerous. Make sure you also have WORKING CO detectors in your house.Kevera, if your hot water tank is going through thermocouples you might have a problem with the gas pressure or maybe the gas valve. Do you rent from Enbridge?

kevera · Post by **kevera** » Wed Dec 05, 2007 8:07 pm

It seems to be a problem with the flame sensor.I clean it twice a year and have to replace once a year.Then it works fine.It only costs $2.99 for the sensor,so no worries there.It could be a thermocoupler,but that sounds expensive.Tankless may be the way to go.

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