I have a colman 7900 series in a mobile home dated 1985 just purchased in Oct 07. The problem is the weather has been warm so shut furnnace off and noticed today the fan is running automatic, I do not want this as to save on electric bill... Do I have a problem and where does the switch need to be in warm weather. :confused:

On simple thermostats there is a switch labeled FAN with two positions ON and AUTO, Make sure it's in the AUTO position.

There should be another one labeled COOL - OFF - HEAT. Make sure that's in the OFF position.

A common failure mode for old furnaces is that the contacts in the relay that operates the fan fuse together.

Usually old Coleman units for mobile homes have a 2 wire thermostat with a change over switch on the furnace. Is this what you have.

I am not sure of switch but I did do the previous answer which was shut to off and leave in automatic and the blower never come bk on so thank you