I had a new YORK 80% furnace installed in Sep'10. Room Temp never reaches required or set temperature- goes up 2 degree and stops. Furnace Flashes red 6 times - "Pressure switch cycle lockout". I have to turn the Thermostat off and on again to restart. Otherwise, it waits for 1/2hr and so and restarts in the meantime temp has dropped by 3-4 degrees. So never catches up with SET temp. e.g. Now it's sitting at 69 while the set temp shows 74! Called the technician, he tweaked the pressure, it went up to 74, he left and we are back to square one. Now he says it's smaller duct problem. Would like a 2nd opinion, any recommendation for Heating expert in LA area? Thank you

Installed less than 4 months ago, should be under warranty, call the installer