I had a Weathermaker Infinity installed in Nov. of 2002(58MVP). I change the filter myself at regular intervals. Other than changing the filter I have had no checkups or service since it was installed. Now for my question. The furnace seems to go on high output a lot. I keep the fan running constantly which makes for an even heat in the house at all times but of course when it goes on high output you can hear the differance. The only thing I am going on here is a guess on my part that this is happening judging from the furnace being in operation for the last three years. In the past it would only go on high when the weather was below 20 degrees or lower outside. The temps around here have been in the forty's for days and the furnace goes on high output more than I think it should. Does this furnace need a lot of fine tuning? Does it need to be looked at before each heating season?