Performed yearly maintenance and safety checks on 22 Bryant furnace. 11.13%o2. 31 ppm co in flu. 0 ppm co in supply. 44 degree deltat. Replaced customer supplied 413 filter. Furnace properly cycled into second stage. Running with 6.81%o2. 32 ppm co in flu. 0 ppm co in supply. 55 degree deltat. Cleaned flame sensor. Blew out water trap. 55 ohm igntion. 55 degree also performed yearly maintenance on York air handler. Founs 10 kw heat kit pulling 20A each. 20/20/40. Customer still hearing dripping. Advised shouldn’t have noise in winter months. Blew out drain poured vinegar customer supplied. Advised more vinegar would be beneficial. May need to address come spring.