Hi,

Just a few month ago I installed new high efficiency furnace and today it failed. The inducer motor would start for about 30-40seconds, then furnace would shut down. Error message indicated that there was a problem with high preassure switch.
As this discussion group helped me here before, I want to share my experience on how it was fixed. I was told that this is very common problem.
I live in Toronto, Canada and here we had very cold few days. I checked outside vents in/out and there were some ice around out vent, I removed it but there was big chunk of ice left on ground and it was touching pipes, just touching, not obstructing holes. When HVAC guy came, he said that if ice is touching pipe, it would make it freeze very fast and you have to remove any contact between ice and vent pipes. We did just that.
Another thing was that HVAC guy checked all small tubes (for aird) inside furnace that goes into preassure switch, disconnected them and just blew into them to take dirt out.
That was enough to fix and furnace started to work.
Just sharing this info if anyone else will have similar problem.

Thanks