Furnace question
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Furnace question
any heating guys out there, my furnace seems to put out hot air when the thermostat is turned down, doesn't always do this, but sometimes the registers are blowing heat and the thermostat is set lower than the room tempeture like something is stuck on, I pulled the cover off the thermostat and the mercury is not making contact, so why the heat? I have my fan on manual so it runs all the time. any help? thanks Randy 
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Is this a gas, oil, or electric furnace? If electric there may be a relay or contactor sticking. If a fuel furnace it may just be cycling after the thermostat is satisfied, this is to remove any heat in the chamber.
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also you may have a bad thermostat , short in thermostat wiring , a stuck relay or jusy possiably like barsbuddy said it could just cycling off
thier is about a 2 minute delay once gas vavle is off before fan will stop if fan is in auto ( fan is in manual )
one thing to check is to turn up thermostat so thier is a call fro heat check to see if burners are light if so turn thermostat down and burners shoud be off if not you got a problem
if so i would say it is working the way it should
thier is about a 2 minute delay once gas vavle is off before fan will stop if fan is in auto ( fan is in manual )
one thing to check is to turn up thermostat so thier is a call fro heat check to see if burners are light if so turn thermostat down and burners shoud be off if not you got a problem
if so i would say it is working the way it should
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I tried what you said tjg, and it seems to work fine, I got the wife to set the thermostat just lower than the room temp and the burners quit, and then set it slightly higher then the room temp and it fires up, so whats up! do you think something is sticking the odd time, and thats why it gets so hot? thanks for your help
Last edited by omni; Jan 1, 2005 at 05:06 PM.
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From: woodland ca
how old is the furnace and what model? is it a standing pilot or eletronic ignition? it could be a bad t-stat, control board, or gad valve leaking by.
if you give me the model# and serial# i could tell what probs they have and what to check another thing is the digital t-stats are inexpencive($20 for the non programables to as much as $200 for the top of the line)and are more accurate. the mechanical t-stats always go out of calibration but are easy to re-calibrate.
if you give me the model# and serial# i could tell what probs they have and what to check another thing is the digital t-stats are inexpencive($20 for the non programables to as much as $200 for the top of the line)and are more accurate. the mechanical t-stats always go out of calibration but are easy to re-calibrate.
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thanks, the furnace is a 1989 RHEEM model #RGDA-100A-EA
ser#CN3D4O4F4288 -- 6272 its been a good furnace, the only problem we ever had with it was about 6yrs ago, we came home and the house was full of natural gas smell, called the gas company and they checked out the furnace but could never determine where the gas had leaked from, I installed a gas detector alarm in the hallway incase it did it again, but haven't had any trouble since. I clean the washable filter once a month, and twice a yr I vacuum out the furnace, I use a rubber peice of hose to vacuum out the burners(they get that white ash build up on them) thats about all I can tell you about it thanks Randy
ser#CN3D4O4F4288 -- 6272 its been a good furnace, the only problem we ever had with it was about 6yrs ago, we came home and the house was full of natural gas smell, called the gas company and they checked out the furnace but could never determine where the gas had leaked from, I installed a gas detector alarm in the hallway incase it did it again, but haven't had any trouble since. I clean the washable filter once a month, and twice a yr I vacuum out the furnace, I use a rubber peice of hose to vacuum out the burners(they get that white ash build up on them) thats about all I can tell you about it thanks Randy
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say the next time it happens run down and see if the burners are still light
or if it is partally light normally if you have gas laeking by valve thier would be some black soot
but if gas vale is sticking then their would be a full flame
if burner is still on and thermostat is satisfied you need to check for 24v ac at the gas valve if thier is 24v and you dont have 24v between grn and terminal w then you have ( is it standing pilot or spark ignition ) iam asuming it is standing pilot then you got a short some where or a bad ignition control module if it spark ignition
if you dont have 24v at gas valve and buners are still on then gas valve is stuck or sticking
or if it is partally light normally if you have gas laeking by valve thier would be some black soot
but if gas vale is sticking then their would be a full flame
if burner is still on and thermostat is satisfied you need to check for 24v ac at the gas valve if thier is 24v and you dont have 24v between grn and terminal w then you have ( is it standing pilot or spark ignition ) iam asuming it is standing pilot then you got a short some where or a bad ignition control module if it spark ignition
if you dont have 24v at gas valve and buners are still on then gas valve is stuck or sticking
Last edited by t.j.g.; Jan 2, 2005 at 09:06 AM.
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From: woodland ca
you have a 100,000 btu gas fired, eletronic ignition. manufactured in nov. 1988.
the ignition control modules are usally the first to go and i change them out alot. usally a stuck gas valve will just leak gas and unless there is a pilot, the burners wont fire up. the gas valves are pretty good in those units i dont remember when was the last time i had too change one. check the boards for any burn spots and water stains
the ignition control modules are usally the first to go and i change them out alot. usally a stuck gas valve will just leak gas and unless there is a pilot, the burners wont fire up. the gas valves are pretty good in those units i dont remember when was the last time i had too change one. check the boards for any burn spots and water stains
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the furnace has a constant lite pilot light(standing pilot), next time it feels like the furnace is putting out heat when the setting on the thermostat is set lower then the room tempature, I'll check the thermostat to make sure the mercury isn't making contact, then check the furnace to see if the burners are lite, could the room tempature needle on the thermostat be out of wack, when it reads say 72 degrees its really say 68 degrees, so if I had the temp set at 69 thinking I'm below 72 its still running does that make sense?
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yea take a thermometer and see if it reads the same as the thermostat
it very possiable that tempature guage on stat is reading high than what the acual room temp is also make sure themoastat is level it not level the thermosat will be way off
or replace it with a eletroinic one 35 bucks at menards
it very possiable that tempature guage on stat is reading high than what the acual room temp is also make sure themoastat is level it not level the thermosat will be way off
or replace it with a eletroinic one 35 bucks at menards
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From: Willamette Valley, Oregon
I have a RHEEM furnace (New last year) The model I have cycles on and off several (3) times an hour, every hour, (just the fan) just to move air around the house. Burner will fire between 1% and 90%, or not at all, depending on the air temp. If the house is warm, and the fan is moving warm air around, the air will feel warm coming out of the registers. Thats how mine works, not sure about your model.
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From: MI
Originally Posted by omni
can you adjust the tempature gauge on the thermostat if it is off after checking it with a thermometer
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Originally Posted by Crash687
Yes you can adjust the temputure poiter on the thermometer part of the t-stat but do yourself a favor and replace it with a digital. Honeywell makes a nice one called the Digital Round T8775. Just swap wire for wire of the R,G,Y & W terminals. no batteries or programming necessary.