Arrived onsite for maintenance of trouble furnace unit. System stopped working. This time it had a code for pressure switch open. Touched the switch and the system started. Performed combustion test immediately due to dancing flame. Found over 700ppm of CO. Pulled analyzer out of flue to protector sensor. Turned system off. Cleaned pressure switch and attached hoses. Measured pressure at from inducer at .72. Fired system up and performed another combustion test. Measured over 800 ppm of CO before removing probe to protector sensor. Measured gas valve outlet pressure at 3.79wc. Rushed to 3.5wc as per label. Removed and Checked flue for a clog. Did not see any. Could not see vent at the top of house for any blockages. Cleaned flame sensor.
