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Re: furnace sometimes will not stay lit
Check the heat exchanger for a crack or hole. The room air blower is blowing back into the heat exchanger extinguishing the flame. Have it checked out today. Did you get it checked yet? Now. Have I stressed to you to get it checked out yet or have you been overcome by Carbon Monoxide yet?
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There is an ignitor and a flame sensor. If the ignitor does not ignite the gas after a time, it goes out. If the flame sensor does not detect ignition the gas valve closes. When you start it you should see the ignitor come on like a light bulb and glow, then the gas valve opens and you get ignition. Then the flame detector turns on when the ignitor goes out. Flame detectors are like a chrome wire that has one connection to it and it sits part of the way in a burner. They get dirty and corroded. When that happens it shuts down. You can clean the flame detector with steel wool of scotch brite pads. Dont get too carried away doing that though.
I am assuming that you are saying that after you have pushed the pilot knob down and the pilot lites and stay lite and then you turn the knob to turn it to ON the pilot goes out...... Then the Gas Valve is bad and will have to be replaced....... Or if you are saying that the pilot goes out when the burners come on then you may need to replace the Thermocouple because the main burner flame is pulling the pilot flame off of the thermocouple and it is weak and will shut the gas off.... Or You could have a cracked heat exchanger that when the burners are on and then the blower comes ON and is blowing the flame around and blowing the pilot flame off of the thernocouple......which will shut the gas off....and then you will need a new furnace or New Heat Exchanger...... These are the most common problems Hope this helps.....
Hi, this motor is the inducer motor, which is the first thing to start on a call for heat. Everything seems to be going through its sequence of operation just fine, but then shutting down on a safety. Look on the panel for a chart that should tell you by the number of flashes and color of the leds what is wrong. It is locking out for some reason, could be several of many. Next to the pilot, you will have a flame sensor. The metal tip sets in the pilot flame. When they get dirty, they will cause the furnace to do just as you say, run and then lock out. You can take a piece of sanding cloth and sand the metal tip on this flame sensor. If this is the problem, it will start and stay running. Also, look for this chart I have told you about, as it is there to help you locate which safety is giving you the problem. My bet is the flame sensor. Please keep me posted, and rate me on my help to you. The flame sensor also has a electrical lead that is attached to it going to the board, so you will see it. Sincerely, Shastalaker7 A/C, & Heating Contractor
Check your filter to make sure it is not plugged. If it is plugged - replace with filter recommended for your furnace. Every manufacture recommends you have your furnace checked and cleaned on an anual basis to keep itrunning safely and at it's top efficiency. If the filter is plugged or the blower wheel plugged, the furnace will shut itself off. Make sure all registers are uncovered - suppply and return registers.
If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts
right back off, then you need to clean your flame sensor with light sand paper
or steel wool. You might need a new flame sensor, but most of the time they can
be cleaned an will work well after cleaning.
First, for those of you who might not know, "What is a flame sensor?" A flame
sensor is a safety device. When your furnace's main burners ignite (light Up)
the flame sensor picks up the heat from the furnace's main burning and says,
"YES," and sends a signal back to the main furnace control board saying that it
is OK to let the main burner stay on. Or if the main burners do not ignite, the
flame sensor does not pick up the heat and says, "NO" to the main control board,
Shut That Gas Valve and Main Burners Down! Thank God we have safety controls
like the flame sensor. Most of the time, after turning your furnace's power off,
you may clean the flame sensors with light sand cloth, emery cloth or steel
wool. Reinstall the flame sensor and you are back in business! Over the years
flame sensors can build up a light coating of burned-in dust and dirt. This
insulates the flame sensor so that it doesn't sense the heat of the flame well
enough, by cleaning it you have almost restored it to its new condition.
Seldom, but sometimes they do go out completely.
Run a wire from the sensor down to the control board conector. Bypass the sensor wire around the connector in the blower deck.
The connection can be wire nutted on the sensor lead with the wire (16 or 18 guage stranded wire works) routed through the blower deck to the other side of the plastic wire connector on the blower deck.
The Sensor operates at high voltage but very low current. The connector will sometimes fail due to humidity or wear.
I have seen this on the Rheem or Ruud furnaces.
Hope this helps.
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.
You probably have a bad Thermo-couple . It is a copper looking rod that sets in the flame of the pilot lite It also has a copper wire that goes to the main valve and connects with a 1/4-3/8 nut or a metal clip. The purpose of this part is to tell the computer that the flame is lit and all is good, but it fails often with the same symptoms.
Be very carefull not to touch the white ceramic igniter, for it will fall apart and that will cost you 40.00 bucks to replace. The last time I replaced my thermo coupler on my furnace, it cost 9-10 bucks and most hardware or heating supply will have it.
. But remember use the proper tools, don't just grab any old pliers, look very carefully and u will be ok.
good luck, mule460