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Furnace burners wait too long to come on

Furnace wait too long to come on and then comes on with big booh and after 5-10 minutes burners and pilot goes off together. I already change the thermocoupler. any advise? Mitchell Manuf. Model 75-AGCF s/n- f1-113

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Sounds like the burners need to be removed from the furnace and cleaned thoroughlyto help with gas distribution if these are in-shot burners they look sort of like an air plane, they have a cross over tube on each side of each burner and if that is rusted up the gas will not distribute evenly from one burner to the next if the pilot and burners go off at the same time then it sounds like you may have some flame blow back maybe due to soot build up in the heat exchanger. Overall sounds like your furnace could use a good servicing

Posted on Oct 16, 2007


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Posted on Jan 02, 2017


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I have a Cozy W355D wall furnace. It's difficult to turn on. Replaced the thermostat, that helped some, but still have to turn it off, wait a few minutes, and turn it back on. Often still won't light.

So are you saying the pilot stays lit, but the main burner won't always fire. If this is a millivolt system you could have a weak pilot flame, not getting the pilot generator hot enough or you could have a weak pilot generator. If you are handy you can try cleaning the pilot. It may be better for a qualified service tech.

Jan 30, 2017 | Cozy Heating & Cooling

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Per landlord, need to light pilot

You would smell the gas, so you're probably ok. Lighting the pilot is not too tough, first you have to get the cover off the furnace. Inside you will see pipes and parts. Hopefully on the cover, inside or out, or somewhere inside the furnace will be instructions.
If not, find a knob that has 'pilot', 'off' and 'run' or something like that. It will probably be in 'run'.
Usually, you have to push the knob down and turn it to get it to the 'pilot' spot. When you do, have something to lite the pilot, which will be inside the furnace more, near the burner. The burner looks like a gas stove or oven burner. The pilot place will be at the end of a small tube.
With the button held down, wave something burning around the burner area. especially at what may be the pilot. The pilot doesn't put out much gas, so don't worry about things blowing up.
Once the pilot has lit, hold the button down for a while, at least a minute. Then you should be able to release the button and the pilot should stay on. If it doesn't, you need a serviceman to come. Let the landlord know the pilot would not stay lit.
If the pilot stays lit, move the knob to 'run' or such, and the furnace should lite, if the thermostat is set higher than room temp. If it has been off, and the room is cool, it should lite.
If the furnace doesn't come on, let the landlord know.
Most landlords have service people for this, it was my job for a long time. Lighting pilots was a common chore for me. If you can, have the landlord send one out to show you how to do it.
As you see, it's not all tough, but it's not all easy, either.

Nov 29, 2013 | Heating & Cooling

1 Answer

Lennox furnace model G11Q3-110 v.2 burners light but go out before fan comes on

Troubleshoot an ignition problem on a Lennox gas furnace ...

? 2:44
Nov 17, 2012 - Uploaded by grayfurnaceman
This furnace should light its pilot with a spark then the pilot proves its on ... Troubleshoot an ignition problem on a Lennox gasfurnace .... Pilot and no inducer but is the same model as that great video! ... You probably have dirty burners. ... How do you know spark module is not sending 24 volts to mv and pv ...

Lennox Furnace Model G11Q3-82-2 -

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Bryant plus 90 intermittent start-up

That's an intermittent problem. Could be: dirty filter, dirty blower wheel, dirty secondary heat exchanger, dirty evap. coil, weak or damaged high temp safety, loose wire connection, fault at control board, poor air flow. Just about 100 guesses! Could be's don't solve anything. Check for cleanliness. Clean flame sensor(flame rod that burner flame comes in contact with). These are the first I would try.

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Janitrol GUPS075-3 Furnace burners will not stay lit

The first thing I would do is make sure the flame sensor is clean, this is a metal rod immersed in the burner flame on the opposite side of the igniter. If too much oxidation builds up on it, it will not allow the burner to stay lit. To clean, just turn off furnace and remove flame sensor and clean with steel wool and then reinstall. If this does not solve the problem there may be a problem with the gas valve.

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Garage furnace (standing Pilot) pilot stops after 30 mins.

it sounds like the afc the fan control not working could be dust on the afc

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Older heater, late-60's gas in mobile home. When furnace ignites it blows back and puts out the pilot light? Also, seems to be a delay when the thermostat clicks to come on til the furnace lights thus...

Check your exhaust pipe for blockage, Make sure pilot light is located just above or below the burner. Make sure that there is a good supply of air going to the burner and that the intake pipe (if it has one) is not restricted. A furnace that old needs to be replaced what ever you find. You could have a cracked heat exchanger.

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1 Answer

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.
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1 Answer

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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1 Answer

Pilot ligting instructions

many of the newer furnaces don't have a standing pilot. look to see if you have a gas valve with a knob on top that says off pilot and on. look to see if a tube the size of a pencil comes out of the valve and goes down by one of the burners, look to see if there is a little gold piece of metal tubing protruding down to the opening of the larger tube . that is where you place the match. i prefer to use a grill lighter. safer and positive flame. turn knob to off wait 5 minutes for any gas to disipate. be sure your incoming gas valves are all open . usually at the meter and one at the furnace. usually the handle is in line with the pipe when open. from the off position, turn the knob on the furnace gas valve to pilot position and push down on it as you turn. this lets gas flow to the pilot tube by the burner where you have you flame starter lit and waiting. once pilot lights hold down on button for 3 minutes or less. longer is better to be sure the thermocouple senses flame . then gently release the downward pressure and the pilot should stay lit and you gently turn knob to on. if pilot goes out you may have a bad thermocouple. be especially careful if its lp or propane as that gas does not disipate like natural gas and can virtually lay on the floor till ignited. also consider having the heat exchanger checked by a pro with a carbon monoxide detector. they do crack after a few years and can be deadly when they do. good luck

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