Cleaned & checked 2 gas furnaces. Inspected heat exchangers & flue venting. cleaned burners & flame sensors. Checked voltage & amp draw of motors. Test capacitors. Main system: Air filter clogged with dirt, causing blower to hit Rev limit. Pressure drop across filter: 1.15 inches water column. Replaced air filter. Clean and check humidifier. checked water flow and drain. Humidifier had no water flowing. I turned supply valve in and back out and valve unclogged. Water flow is currently fair. Humidifier pad coating ineffective. Replaced pad. Blower: 4.3A . Inducer: 0.26A . Lower level system: Replaced air cleaner media. Blower: 2.8A. Inducer: 2.17A. Suggestions: Run main system blower continuously for a couple days for humidity level to recover.