Came out today to inspect a Lennox furnace not heating properly. Model #SL280UH090V36B-03, serial #5915D00606. Upon arrival the homeowner stated that since the storm the heat has been working sporadically. Upon arrival I noticed the system had an error code for low pressure. I reset the system and observed the system try to start normally.I found a mechanical fault with the exhaust removal system. The system is under warranty for parts. Price quoted by PA for repair. No arrival fee per dispatch.