Gas furnace; flame will not stay on

Fix Furnace Flame Sensor (Flame That Goes Off) - YouTube

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https://www.youtube.com/watch?v=fBJ3r9MUa-U
Nov 29, 2011 - Uploaded by RochNoure
A Furnace Flame Sensor is a safety device that reads the temperature and ... easy fix, but the furnace is ...

Troubleshoot the ignitor of the Rheem RGDA model gas ...

? 5:53
https://www.youtube.com/watch?v=Bx1pXONg2Oc
Dec 12, 2012 - Uploaded by grayfurnaceman
Troubleshoot the ignitor of the Rheem RGDA model gas furnace.... Jun Sim 5 months ago ... My lennox ...Missing: lx2000

Rheem Criterion II No Heat - YouTube

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https://www.youtube.com/watch?v=yOSk6qvpWbA
Jan 7, 2010 - Uploaded by Work12Progress
Rheem Criterion II gas furnace model # RGPH-07EAMGR. When a call for heat is made t wo green led's ...Missing: lx2000

Heater will not kick on unless... [Archive] - Self Help Forums

www.selfhelpforums.com/archive/index.php/t-2153.html

Oct 19, 2004 - 25 posts - ‎9 authors
After a certain amount of time of not running, the heater will refuse to kick back on. ... 2 flashes, then a 2 second pause = pressure switch is open. What do .... On LP gas furnaces, the spark starts and the gas valve opens. ... Buffing them up with a little steel wool (5 minute job) is a good annual PM thing to do.

If your talking about taking out the flame proving rod and cleaning it with sand paper or abrasive cloth and that didnt work, you may have a bad flame proving rod and it needs replaced. If the flame sensor is good, it could be the board not keeping the call to the gas valve, the gas valve not keeping the call, or your thermostat not keeping the call. Hope this helps narrow it down.

There are several things that control the gas valve. A bad flame sensor could cause the valve to shut off upon initial ignition because it's not sensing the flame.

The high limit sensor would shut the unit down only after the unit was runnung for a period of time. It senses the temperature of the heat exchanger. Now if it was bad it wouldn't allow the gas valve to open for ignition.

the only other issue could be with the induced draft blower motor not running.

It it seems to me that the flame sensor is the problem because of the short time your unit runs.

I would have the ignition control board replaced. That is what tells the gas valve to come on and if there is flame or ignition it will keep the gas on if the flame sensor gives the board a signal that the burner is lite. By you shuting power off and on to the furnace it resets the board and it will go through its cycle again.

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, so by cleaning it you have almost restored it to its new condition. Seldom, but sometimes they do go out completely.

In the path of the flame on the last burner that starts, there will be a small rod. That rod is the flame sensor. Take a scrub pad and polish it. Also check the electrical connection that goes back to the circuit board. Disconnect any ground wire from the circuit board to furnace cabinet, sand it and replace it.

Have the thermocouple replaced, ensure the pilot flame is blue - not yellow, yellow indicates blockage in pilot

This sounds like a bad heat exchanger. It is possible that you do not see the crack because the crack is closed when the heat exchanger is cold (or room temp). Allow the furnace to heat up, this will allow the expansion of the crack. Turn the power off and examine the heat exchanger while it is still hot.

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.

Goodman gmp075-3 gas furnace and the flame cycles for 4 sec