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Anonymous Posted on Oct 06, 2014
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Pilot and burner light then gas shut off model 7900

Pilot and burner light before furnace reaches thermostat tempature pilot and burner go out

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Jack Black

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  • Posted on Feb 14, 2015
Jack Black
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How many degrees before it reaches desired temp, does it shut off? A thermostat is designed to shut the furnace off a couple/ few degrees before it reaches set temp. It has what is called a heat anticipater, which shuts the burner down, and lets the blower use the remaining heat from the heat exchanger to bring it up to desired temp making it more efficient. If it is more than a few degrees, replace the thermostat. You can jump out the red and white wires to confirm the faulty thermostat. If by doing this, the furnace never shuts down, until you separate the red and white wires. That confirms a faulty thermostat. Hope this helps someone.

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Ken Bledsoe

  • 306 Answers
  • Posted on Nov 24, 2008

SOURCE: Coleman Propane Furnace Good pilot light but feed/ignite main burner

If you have a volt ohm meter take the two leads off the gas valve and ohm out the connection should have resistance for the coil. You said you have 12 volts from the thermostat white and red in the heating mode you should have minimum 26 volts. If you want to check the transformer should have 28 volts. Almost sounding like the transformer is getting weak. You can get parts for a 20 year old unit at any HVAC parts house. Try Washer Specialties here in Wichita Kansas they are on the web. Lowes even carries Transformers. Has to be rated 120 volt primary side secondary side 24 volts and 40 VAC.

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Dale Koehn

  • 88 Answers
  • Posted on Jan 20, 2009

SOURCE: furnace blower not working how it should

first off buy yourself a honeywell stat, in my personal opinion lux stats are garbage, I have run into so many that are bad stats !!! but as far as your fan not shuting down, sounds to me like your fan center on your circuit board is bad and will not shut down the fan when needed, you will have to replace the circuit board, as the fan center is a part of the whole of the circuit board, hope that helps

Anonymous

  • 92 Answers
  • Posted on Feb 26, 2009

SOURCE: gas wont ignite

unless you are well trained in troubleshooting you need a pro .carrier furnastys are overly complex you should call carrier dealer if you want the shortest route to a workin system

Anonymous

  • 1187 Answers
  • Posted on Sep 16, 2009

SOURCE: COLEMAN FURNACE BURNER NOT LIGHTING

There is a thermocouple "wire" that is supposed to be touching the pilot flame.
The thermocouple senses a flame (hot) and allows the heater to operate. If the thermocouple does not sense that the pilot is on, then it will not allow the furnace to operate.
Bend the thermocouple wire (or the pilot tube) so that the pilot flame is touchingg the thermocouple.

That shouls work now.

The air from the fan should not be blowing through the same cxavity that the pilot is in.
If it is, then you may have a leaking furnace whereby carbon monoxide may be seeping into your living quarters.
If the fix above works and the pilot stays on after the heater starts, then there is probably no leak.

Let us know the results ... post a comment or "RATE" this or another expert's solution.

Paul Carew

  • 3808 Answers
  • Posted on Feb 05, 2010

SOURCE: I have a coleman evcon model dgat070bdf furnace.

Hi check the flame sensor is clean also check out the pressure switch , and check air filter is clean

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Furnace reaches temperature set then shuts down and restarts 8 times before final shutdown.
When you say the the furnace re-starts 8 times before shut down, what is cycling 8 times? just the indoor blower or is the main burner re-firing 8 times? If it's only the fan it sounds like the fan control.
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Mar 07, 2018 • Coleman Heating & Cooling
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My pilot stays on on my propane furnace but will not light up
The Little Giant units use a Unitrol gas valve very similar to a water heater in the home. #1,urn the Unitrol gas valve to the "PILOT" position to ignite the pilot. Depress the plunger and hold it down then push the spark igniter button until you can see the pilot flame ignite.
You have a lit pilot so this is not a problem for you.
The pilot light stays on continuously by design.
Once the pilot flame is established, you then turn the on/off/pilot valve to the "ON" position and set the thermostat to the desired temperature range., it should then fire its main burner until the desired temperature is reached. Once the temperature is reached, the main burner will shut off and the heater will go into a standby mode with the pilot flame still burning.
If you have turned the pilot valve to on and set the temperature high, it should come on, if not a new gas valve is required, they can be very difficult to replace due to rust.and most cases require a new unit,
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Mar 19, 2015 • Unitrol Propane Heater Valve - Little...
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I have an early 80's mobile home with an "intertherm gas atmospheric furnace" pilot light is lit but can't get the furnace to "fire". Seems as though the limit control is stuck open. ...
If your pilot light is lit then I would first check your thermostat. Make sure it is on heat setting and fan is on auto, turn stat up to where it should be calling for heat. If you don't get burner to light remove front cover from thermostat and see if it has a mercury switch, if it does move temperature selector up and down and see if you can see a spark in mercury switch vial. If y ou cannot see a spark remove screws that attach t-stat to base.Remove carefully and disconnect wires that go to r and w terminals on stat base. Temporarily connect these two wires together. This should make burner light if you have power to thermostat. If burner does light disconnect wires and replace thermostat. Also if you have a volt meter check across these two wires and see if you have power there. Should be around 24 volts a.c. If your thermostat has a fan on setting try that. If fan runs you know you have power to furnace The gas valve needs 24 volts to operate and inside the electric control box in furnace there is a transformer to step down 110-120 supply voltage to 24 volts. If transformer is working you should be able to hear a low buzz or humming sound. You can also check across gas valve terminals when t-stat is set for heat, you should read about 24 volts. If you have 24 volts to gas valve and it is not opening then you need to replace gas valve. The main purpose of the limit switches is to turn blower on when temperature in heat exchanger reaches fan on temp,shut off blower after burner shuts off and heat in heat exchanger reaches fan off temperature, and limit if temperature exceedes set point without blower coming on. I hope this helps you. Thanks
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Nov 25, 2010 • Heating & Cooling
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My Rheem Corsaire furnace is short-cycling. It ignites, the burners stay lit the fans run for a while then the burner shuts off, the fans run until the cooling oft temp is reached then shut off. Right away...
Try blowing air thru the pilot tube. You may have a spider web in the burner tube.
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Oct 15, 2010 • Heating & Cooling
0helpful
1answer

Im trying to figure out how to light my neighbors 7900 series gas furnace. Followed instructions pressing pilet light etc. Just cant figure where to ignite inside furnace door.
Hi, Just follow the pilot light tube back, the aluminum tube, back under to where it stops at the pilot burner. You may need to open the door to reach back there or you may have that piece of metal that you put the match in to reach back far enough to light it. Just turn the knob to pilot, and hold it down and you should be able to hear and smell the gas. Light the match and stick it along side of the pilot tube at the very end and it will light as long as you hold the knob down. After it lights hold it for about another minute and release it slowly. It should stay light. If not wait 5 minutes and try again. Very easy to do when you follow the tube that supplies gas back to the pilot, that's where you stick the match or lighter. Look back there with a good strong light and you can see where the tube stops. This is where the gas comes out. Please let me no, and don't forget to rate me as I know you will be kind. You will find it. If you can't get it, you can call out your local gas company and they will light it for free of charge, no cost to you.
Sincerely,
Shastalaker7
A/C, Heating Contractor
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Sep 18, 2010 • Coleman Heating & Cooling
1helpful
1answer

Furnace cuts off before reaching set temp.
You can make sure it is not the thermostat by crossing or jumping the R and W terminals (or associated wires) together. This will keep the furnace calling for heat. As it is approaching set temperature, get in front of the furnace and inspect the air filter to make sure it is clean, watch the control module for any error codes that may be turning off the system prematurely.

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).
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Mar 07, 2010 • Honeywell Programmable Thermostat Heater
2helpful
1answer

Furnace tries to light but misfires
Check the air filter.
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).
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Feb 26, 2010 • Goodman Heating & Cooling
0helpful
1answer

Lighting the pilot light
The steps involved can vary slightly depending on your furnace model and pilot valve type, so if possible try and find the instructions inside the furnace door cover or in the instruction manual. This is for a gas fired furnace, but applies to any gas-fueled appliance including water heater. Two of the most common types of pilot valve body assemblies either have a red reset button and a gas valve or no reset button and a valve knob that can be depressed. But whichever type you've got, if you have an older model furnace with a standing pilot (flame is lit all the time) then this is the basic procedure.
  • Turn you thermostat to 80 degrees or to a setting that will demand heat. Make sure the thermostat is in "Heat" mode.
  • Go to the furnace and find the pilot valve. The pilot valve body is a box shaped device into which the main gas line will run and is located near the gas burners. It will usually have a gas **** or valve knob that reads "On, "Pilot" and "Off." Locate this gas **** or knob.
  • Turn the knob or gas **** to the "Off" position and wait about 3 minutes for any residual gas to clear away.
  • Find the pilot. It's located near the gas burner tube assembly in the furnace.
  • Get your match or lighter ready. Sometimes the pilot is hard to reach. If possible, try and use a long fireplace match when you light it. If you don't have a fireplace match then a butane BBQ grill lighter works well too. If you don't have that, then you can fasten a match to the end of a stick when you light the pilot
  • If you have a pilot with a red Reset button, turn the gas valve from "Off," to "Pilot."
  • If you have a pilot with no red button, turn the knob from "Off" to "Pilot."
  • Place the lit match or ignited lighter tip at the pilot and depress and hold the button or depress the knob as appropriate. Depress the button or knob for about 30 seconds. This maintains gas flow to the pilot until the thermocouple gets hot enough to open the main gas valve.
  • Once the pilot stays lit, slowly release the button or knob and turn the gas **** or knob from the "Pilot" position to the "On" position. This will ignite the burners and keep the flow of gas supplied as required for the burners as called for by the thermostat.
  • If the burners fail to ignite then it may be because the thermocouple did not get hot enough to open the gas valve. Wait a few minutes and then repeat the above procedure. This time hold the red reset button or depress the knob for about 45-60 seconds.
  • Once the main furnace burners ignite, adjust the thermostat to the desired setting.
  • If you've followed the previous steps on lighting the pilot and it still does not light after, or will not stay lit, then you probably have a problem with the thermocouple or an adjustment needs to be made to the pilot. You'll need a furnace service technician to replace or repair these parts. You may find that the pilot lights, but it is an anemic looking flame. That's a different problem we'll look at in the next section.
  • If the pilot lights but the flame is a weak yellow flame, it will not get hot enough to heat the thermocouple to its set point allowing the gas valve to open.
    A natural gas flame should be a bright blue with the tip of the flame having just a tinge of yellow. A propane flame should have a bluish green flame with a tinge of yellow at the tip. The flame should be strong enough to hit the thermocouple tip about 1/2 inch from the tip end. If the flame is weak or shaky looking, check to see that a breeze or draft is not blowing on it. Adjusting the Flame
    There is usually a small screw on the pilot valve body that will adjust the flame. You may have to refer to the manufacturer's instructions to find the screw. Turn the screw as needed to adjust the flame throw. Yellow Flame
    A yellow flame is caused by lack of air and incomplete combustion. It can be caused by a dirty pilot tube tip. Split Flame
    This is caused by dirt in the pilot tube. Take a needle or small nail and gently clean the tube. Flickering or Wavering Flame
    A flame that flickers is usually caused by a draft.
Thanks for using FixYa - a FixYa rating is appreciated!!
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Feb 18, 2009 • Water Heaters
0helpful
1answer

Rheem gas furnace pilot lights, but no burners or fan
If the burners do not fully ignite, the sensor will shut the furnace down. The lack of sufficient burner flame is a gas valve or gas pressure problem within the valve.
Replacing the gas valve with the original one may get you going. I surely suggest a professional service company for safety reasons and a thorough inspection. A 20 year old furnace is past it's normal life span.
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Jan 06, 2009 • Heating & Cooling
0helpful
1answer

Mobile home furnace
you probably have a bad thermostat if it wont shut down id replace the thermostat first and then have the thermocoupler checked...replace the thermostat
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Aug 20, 2008 • Heating & Cooling
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