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I have a problem with my heating system. It is about 10 years old and has had the ignitor, combustion blower motor, and programable thermostat replace in it's lifetime. The system worked great last year. This year has not been so good. The system was checked and cleaned last month. What is happening is the blower kicks in and the burner cut off after a few (15-20) seconds. I tried shuting down system and turning off power to reset. When you turn heater on this is what happens 1. Combustion fan comes on for 35 seconds 2. Ignitor fires about 14 seconds 3. Gas vavle opens and ignites. Burner runs about 45 to 65 seconds and goes out. 4. Relites in about 45 seconds, this cycle repeats several times. 5. Main circulating blow comes on and about 20-30 sec burner goes out.Then the blower cuts off, a little later 30-45 seconds the burner relites and we start all over again. The temp inside of house will not go above 63 no matter what you set thermostat at. System can run all night but never cuts off. The unit uses LP Gas, No codes on control panel. System Model# MMBB090ABHR06. Temp at vent 79-83 when blower runs.

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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.

Posted on Nov 21, 2008

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