Furnace running past thermostat setting

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I have a Coleman model 2775C766 furnace installed in 1989. For the last three years during the winter, the furnace will kick on at the temperature set on the thermostat but intermittently will continue running. The thermostat is set for 70 and I will come home and the house will be 86 degrees with the furnace still running. I don't know how high it will go because I've always caught it running and 86 has been the highest so far. The furnace has to be turned off by the switch on the furnace, it will not turn off simply by turning the heat off at the thermostat. This may happen two times in a day or night but then will not happen for a few days in a row, then will start doing this again. We have had a furnace company out a few times but they cannot suggest anything because this has never occurred while they are actually here. We changed the Honeywell programmable T-stat to a standard Lux model. The hot surface ignition module has been changed. We are leaving for vacation at the end of this week and I want to know what will happen if the furnace just keeps on running as no one will be here to turn it off (although someone will be stopping by intermittently). Could this be the gas valve sticking? I would appreciate any suggestions from you that I could relay to the furnace serviceman.

Thanks, Elaine

-- Elaine Gierada (eag1952@earthlink.net), February 16, 2004


elaine. some things to check. t-stat wireing that red and whiter are not crossed. sticky valve, sticky relay in the ignition module. pull one wire off the gas valve and see if it shuts off. if it does the problme is electrical. if not it's mechanical. could be dangerous especially if the fan fails, limit fails. old hoot. Matt. 24:44

-- oldhootgibson (oldhoot@shawneelink.net), February 18, 2004.

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