Cleaned & checked 2 gas furnaces. Inspected heat exchanger & flue venting. cleaned burners & flame sensor. Checked voltage & amp draw of motors. Test capacitors. First floor system: flame sensor current dropping below minimum. Clean flame sensor and tested: 2.7 micro amps. Replaced air filter. Blower: 6.6A . Inducer: 1.38A . Gas pressure: 3.4 inches water column. Temperature rise: 47 . Supply: 114. Return: 67 . Second floor system: Replaced air filter. Blower: 5.8A . Inducer: 1.45A. Gas pressure:3.4 inches water column. Temperature rise: 46 . Supply: 115. Return: 69 .