Heating Problem

[grodzewicz]

I have a Coleman Model 7956A856 With a Nordyne 901649 Heating/Cooling Blower conversion for the addition of central air. Yesterday the heat went out and I found it to be the limit switch by the blower. after resetting the limit switch the furnace functioned. several times during the next 3.5 hours of continuos running to bring the temp up from 53 degrees in the house. I heard some squeeking and a few screechs from the blower/squirrel cage area. Today my wife called me to tell me the heat was out again. I told her abouth the limit switch, she reset it and the furnace functioned for a few minutes then the blower quit but the burner stayed on and the limit switch was not tripped. after a while she checked it and the limit switch had tripped and the burner had gone out. she reset and we had heat again. When I got home she also told me that the blower housing around the squirrel cage had gotten very hot. could that have been caused by the burner running and the blower not moving any air or by the blower motor over heating. I do not know how long after the blower turned off that the housing was hot or if it was hot when the motor quit working. My question here is, Is my blower motor on its last leg or could there be some other problem. Any help or ideas will be greatly appreciated as it will be below 20 degrees at night up her in michigan.

[Old Guy]

Very difficult to diagnose in cyber space, but the screeching you described would indicate the blower and/or fan bearings are gone. The limit switch turning off the power to the burner was just doing its job, because it got too hot in the compartment since the blower wasn't functioning properly.
Can't guarantee this, but it would sound like the problem is in the blower motor. If you can get to the squirrel cage, try turning it by hand and see if there is unusual resistance. Oh TURN OFF THE POWER FIRST!
Unless you have the proper meters and experience to test further, I would strongly suggest calling a professional. At least you will be able to tell them if the fan turns normally.