My name is wally 213. My Whisper Heat by Lennox starts up with a big bang. Then it seems to run fine. The SER. Is 5893A12778 It sounds like it could be very dangerous and I need to know what the problem might be. I hope you can help me. The furnace is 17 years old, so it could be a number of things.

I suggest you contact a Lennox service company NOW. The big bang is something you do not want to try and fix yourself.

The whisper doesn`t whisper anymore

I hope you as the homeowner don`t go out with a bang,, yes get it looked at, yesterday if possbble it's that serious

Dirty burners will do it every time. Its time for a service.