I have a ruud furnace and it won't turn on when set on "auto" mode,its only turning on in "manual" mode and blows heat.The fan turns on when put in the "on"/"fan" mode. I have to turn it off manually once the rooms have reached the desired temp.I could here the blowers start than they shut off automatically after a minute or two. There is heat coming out of the egsaust vent on the side of the unit and I'm hearing a noise comeing from the area near the blowers.