I have a York (Coleman) TM9X060B12MP11B furnace that is about 7 years old now.
For years I have had the issue that if it's cold outside, and often when it has been snowing, in the morning it kicks on, heats for a while but then stops.
The error codes flash 6 times, which means:
6 RED FLASHES: This indicates that after the unit was operating, the pressure switch opened 4 times during the call for heat. If the main blower is in a “Delay on” mode, it will complete it, and any subsequent delay off period. The furnace will lock out for one hour and then restart.
Every time I have to wait an hour, then it will heat for a bit until the house is at temperature. Usually that's the last of it for the day, in the afternoon and evening it's fine.
When it happens I use a chimney cleaner to make sure no snow built up in the exhaust or intake pipes leading outside.
The furnace is positioned in the middle of the house with a run of about 40 feet leading outside (row house) with 2 small 45 bends to get it in the ceiling
The question I really have is, what does the pressure switch do? I see stories online about it triggering because the drain is clogged, but what drain would this be?
Does the pressure switch trigger because it can't get enough outside air in, or does it trigger because it can't get the exhaust air out quick enough?