I put up a thread like a week or so ago but can't find it now. Any ways, my furnace will not work. I tried doing what a poster replied but it didn't work. He said to coil in front of the pilot. Well there is no pilot , just a coil that glows and start the fire to the burners. I tried removing the flame sensor rod and cleaning it but that wasn't the problem either. Any other ideas?
what's the model and make of your furnace? i had a problem with my furnace last fall so i did some research. ultimately, i ended up hiring a HVAC tech to look at it because i didn't want to blow up my house. however, after a bit of research... here is the basic sequence of an 80% efficient gas furnace: 1: call to heat from thermostat, draft inducer turns on to clear the furnace of any residue gas. if flu vent is clear, the inducer will cause a pressure switch to close (pressure switch won't close if vent is blocked). the pressure switch is usually connected to a relay switch. the pressure switch may be burnt. some switches have a pop up button. 2. after cpu gets the signal draft sequence is running without problems, it opens the gas valve and lights ignition (the glowing thing you've described). the draft inducer should still be running. there's also a flame sensor close to the gas manifolds (trumpet looking pipes in back of the ignition). the flame sensor looks like a bent think wire. if it doesn't sense flames within a set period of time, the furnace turns off, but the draft inducer will still run for a few minutes. problems could be that gas is not turned on, ignitor broken(not in your case) of flame sensor is broken. 3. if the cpu gets an ok from the flame sensor... meaning there's gas burning, it turns on the blower. the blower blows cool wind into a heat exchange (like the radiator in your car) and hot air goes out ducts to your house. the cpu will shut down the sequence if the blower is malfunctioning. judging from your description (and assuming your furnace works the same as mine), it could be either a relay from the pressure switch burnt (~30$), blocked flu vent, broken flame sensor (~30$), gas valve not working(donno $), malfunctioning blower (?$) or cpu malfunctioning (~100$ on ebay). if i were you, i'd get an certified HVAC tech to look at it. while furnaces are fundamentally simple machines, you're dealing with gas.
thanks. I am familiar with the workings of gas furnaces but am in no way a Hvac tech. I am guessing my flame sensor might broken. The gas valve works cuz it release gas after about a minute of the vent fan blowing..... the glow rod ,glows, flames appear, go for a few seconds then all stops. I guess I will have to get a tech to ID the prob for me. I just hate paying people to do stuff I can do myself.
Actually I didn't do that. I figured the vent fan blows for like a minute before the lighting sequence with no problems that it probably isn't that. And it has a grid like on the flue , so I thought it would be hard for any foriegn object to get in there. Well I will check it out tonight.
The original problem you described was the exact same thing I experienced. Mine was blocked with snow (doubt that is your case), but yours could be blocked with someting else (leaves, raccoon, etc.)
