arrived on site to diagnose a no heating unit. Client stated they heater is not blowing any hot air out and it’s just cold air. Cycled unit on and sequence of operation did not complete itself. Started testing parts. Found the pressure switch was not closing. Inducer motor would keep running until a lock out. Tested pressure switch and manually got it to close as I pulled air from switch. But inducer could not close switch. Traced back to ventilation. Checked b-vent for n furnace and roof. Found nothing was clogged up. Tested inducer pressure. Found it was not pulling enough to close switch. Removed b-vent to see if ventilation was issues and cycled and unit still didn’t close switch. Verified with manometer inducer was pulling 0.6 and pressure switch was rated for 0.65. Advised and verified with supervisor and he did stated inducer may just not pulling enough to close it. After running bad for so long pressure switch may have gotten weak and now just fail from it not turning on f