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Czarme69 furnace turns on blows fire for a few seconds then just blows cold air, doesnt heat to temp on thermostat

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Re: czarme69 - Heaters

Need make and model number

Posted on Dec 29, 2007

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Furnace in mobile home has a few problems

Sounds like fan & limit control
If temp on limit reaches max temp what happens gas valve deenergized,as MTR continues to run begins to lower temp. Thus reenergizing valve
Check filters,MTR speed for heating

Feb 03, 2014 | Coleman Heaters

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Heil furnace blower motor stays on won't shut off at thermostat blows cold air continuously

Do you have t sat fan switch in on position??? If so blower will run continously set it to auto and it will cycle with heat call

Nov 12, 2012 | Heaters

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SO basically my furnace just stop kicking on the heat at some point last night. I have it set on an auto temp around 70. By the time I noticed it being cold in the house I went up to the thermostat and...

I want you to do a simple test to verify that this is a thermostat problem for me. Start by removing the thermostat from its' mounting, next locate the red and white wire terminals place a jumper between them. If the heater now runs it is the thermostat went bad on you, if it does not run please check all connections both to the thermostat and to the furnace making sure that your wires have tight connections and are not broken. I am really leaning towards the thermostat being bad here. Sorry for the bad news but really strong feeling. Good luck

Jan 12, 2011 | Goodman Heaters

1 Answer


Heat pumps tend to blow a much lower temperature outlet air than a gas fired unit would. Is this your first year with this furnace?  Depending on your outside temps, an auxiliary heat strip may not be operating properly. 

Jan 05, 2010 | Heaters

2 Answers

Gas furnace is constantly blowing cold air

An indoor blower running when it is not supposed to usually indicates an overheat condition. I would guess that it has been cycling on and off for some time and finally caused the high limit to stick and not auto reset. if you tap it sometimes they reset. the real problem is that it has been overheating from lack of airflow, over sized unit, not enough return air, too many closed registers, dirty filter, dirty squirrel cage blower and or air conditioner a-coil. If you get it started again sit and watch the unit run the flames should come on and stay on for the entire heating cycle, not going on and off.
I wish I could help you more but it is difficult without seeing the problem myself. Good luck! this should get you started!

Nov 01, 2009 | Heaters

1 Answer

Coleman gas furnace. Burner will re-fire for a few seconds during the cooldown. Model G8C07512MUB12A

This is a little complicated because it can be several things and you need to provide more specific info....It could be your furnace is shutting off on the High Limit...which means your furnace is running too hot...check the filter , return air vents etc would be an airflow problem...dirty blower....Furnace can be too big for your house....when the furnace shuts off on High LImit , the fan will continue to blow air , cooling it down as usual and once the furnace cools enough to reset the high limit trhe furnace will Ignite again as long as the thermostat is still calling for heat . The furnace could also be running too long and getting too hot....your Ductwork can be too small...many factors come into play

Oct 25, 2009 | Heaters

3 Answers

Furnace with cold air only

Sequence of operation, Gas Furnace.

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 ignitor. The ignitor will glow and you will be able to see it if viewed thru the small inspection port. Once the ignitor 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 ignitor does not energize (bad control, bad ignitor), the gas valve does not open or there is no gas (bad gas valve, broken wire, no gas), the pilot does not lite (dirty pilot), the burner does not lite (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).

Most newer furnaces will have a diagnostic center or control built into the control module. You may be able to view it as it is running thru a small viewing port. Some models will require the removal of an access panel prior to finding it. On the reverse of the access panel, there will be a diagnostic chart that will aide you in understanding any error code recorded (usually a blinking light).

This is why we technicians earn the big bucks!

Dec 07, 2008 | Goodman GMS90703BXA Heater

2 Answers

Blower works but no heat

If in fact you have the above listed furnace, you do not have a pilot but electronic ignition. You will need to remove the front cover on the furnace, tape down the door safety switch and then have someone help you by turning up your thermostat to a very high setting. Watch and listen inside the furnace. There should be some blinking going on at the control board followed by a small blower fan starting up. Then after 10-15 seconds there should be a click followed by an orange glow viewed thru the viewing window to the burner section. In a few seconds the gas valve should click and the burners will ignite. There is a safety switch that will sense flame and then keep the gas going to the burners. If it does not sense it, it will shut it off within 10 seconds. If all is well so far, your blower will turn on in about 90 seconds after flame. There is a diagnostic code chart on the back side of the access door if you get an error code (blinking) on the control board.

Always check little things like air filter, condensate drain and broken or loose wires.

Nov 05, 2008 | Goodman GMS90703BXA Heater

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