Arrived to find unit unplugged, I plugged it in and gave a call for heating. During cycle it was discovered that unit was tripping out on high temp. I adjusted gas pressure down .6†to 3.2 as well as increased speed of fan. Found several vents closed or obstructed I advised customer that ALL vents must remain very poor airflow reasons to believe duct work is part of the issue. Also dirty blower wheel as well as secondary heat exchanger, a coil probably needs cleaned