My Comfortmaker enviro plus 90 fan blows ALL the time:confused:. Ive changed the batteries in thermostat no change:(. Ive taken the thermostat off the wall while it was running no change:confused:. I just purchached a new programmable thermostat today, installed it and the same, no change:mad:. There's no change in the temp even with it on heat or cold from the highest to the lowest temp:mad:. As of now I turn the unit on and off at the source. It started at the end of winter - beginning of spring earlier this year. Please help if you can. Thanks.

If you can find your circuit board in the furnace see how many blinks happen on the trouble light and then look at the inside of the blower door for a answer to the number of blinks.

It has no lights on mother board. The fuse is good also. Could it be a (the) relay switch?

And how should I know if the furnace pilot light is light?

I do not believe you have a pilot that is lit manually. You have a form of auto ignition probably HSI.

I thought you were having a problem with the blower and now mention (( and how should I know if the furnace pilot light is light?))

The blower could be a relay and if your circuit board has a relay on it for the blower it could be bad. There could also be another relay mounted to the furnace off the circuit board. LOOK on the back side of the blower door panel for a wiring diagram. All furnaces have on there and trace out the circuit.