Problem solved..... the Tempstar did not have an adjustable high/low limit switch like old hot air furnaces. I cannot control when it switches on or off. The fan control is set by moving a spade connector to one of 3 settings. Hi/Med/Low. I moved it down to Med. and the results were satisfactory so far. The air no longer hisses and makes tons of noise and the air temp is higher coming out of the registers. I will have to watch to see if it cools the house next summer but I think it will work the same in reverse. Thanks Larry, my experience with AC is zero, my experience with propane furnaces is higher then most homeowners, but I did not know how this combo unit was set up. Turns out it was just another ho hum deal, take it apart, look at it, figure it out. I was just thinking someone had done the same thing and wanted to increase the learning curve or avoid any pitfalls.