Pilot stays lit, main burner lights, heats to fan cut in temp and fan starts. The fan runs for a few min then stops and the over temp safety cuts in and the gas is shut off. Fan bearings are good and the fan runs freely. Solenoid has been replaced but no difference. Bridged the cut in switch, without the burner and the same thing, fan runs for a few min then shuts down. Bridged the safety cut off without the burner and same thing, only a few min run time of the fan. The only thing not replaced isthe resister and fan motor, but it runs smoothly when it runs.
You need to check the volts at the motor while it's running, to make sure some safety is not shutting it off. Then check the amps on the motor while it's running. Also you need to check your capacitor and wiring.
SOURCE: I have a problem with
sounds like its not proofing flame. it has a sensor usually like a needle sticks out into the flame that tells the gas valve the flame lit and is burning so its ok to keep sending gas, if its fails to proof flame then burner shuts down, then it tries to relight 3 times then locks out on fail safe. the blower will sometimes run continually once that occurs to highlight a failed condition. every time you reset it will try again 3 times then shut down. lp gas is very dangerous, even i do not work on it as the gas acts like gasoline and lays around. not like natural gas that disperses well. if you see the flame sensor try gently cleaning it with a little emory cloth. also a loose ground can cause this. check tio be sure any green wires are snug , they actually flow volts to ground through the flame on some to proof, thats why no ground no flame. if that fails then the board is most likely problem. change wire for wire , or get generic replacemant and follow directions exactly. good luck.some ignitors act as a flamre proofer as soon as they are done igniting! rarely do they fail to perform both funtions.
SOURCE: I am working on an older reehm furnace a corsaire.
either the sensor is dirty or bad,clean the sensor first if that doesn'y work replace it
SOURCE: Furnace runs about 1 minute, then total shutdown
What type of gas supply line do you have? Is it black pipe or copper? If it is copper, there can be a film like substance that builds up on the inside of the copper. The debris will the get caught in a pre screen where the supply enters the valve thus cutting the supply of gas to the unit. Also, the thermocouple may be bad. You didn't say that you replaced it. Try replacing it as well. Also, you could have a limit switch turning the system off and thus cutting the gas off completely but it is highly unusual for the pilot to be cut off as well unless the pilot is being blown out when the gas is shut off. Also, turn the unit to fan only without calling for heat. Using a flame of some sort, put it into each baffle of the heat exchanger. If your flame is being blown around in one of the baffles, then you have a hole in the heat exchanger and what is happening is that the roll out switch is cutting the unit off and the air still moving through the heat exchanger is blowing the pilot out. I have seen this actually happen. If your furnace is in excess of 15 years old, it does need to be checked for possible holes. If it is in excess of 25 years old, it is a huge possibility that the unit has already developed a hole. If you feel hair coming out of one of the baffles, then shut the unit down immediately and have it replaced!
SOURCE: gas furnace, main burner ignites the other 2 don't. then shutdn.
Between the burners is a small rail in the pressed steel where the flame runs across to light the other burners and it sounds like there is dirt or debris in the step over rails causing the problem. You will need to use some compressed air on those rails to clear them out. Once the rails are clear the other two burners should ignite right away.
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