21 year old Lennox Gas Furnace - No Heat System not heating due to age, 21 years old. The main control board has failed and is flashing random error codes. The high limit is burnt, the heat exchanger is compromised, the inducer motor is over amping, the blower wheel is dirty, the blower motor is over amping on start up and run, the igniter is weak and chalky, the flame rectifier is also chalky and reading below manufacture parameters. At 21 years old all parts are subject to failure on this equipment. Due to the age, I recommended updating the equipment. Scheduled a 11-2 appointment tomorrow for our install supervisor to come out and go over updating the equipment. Thank you for choosing T.E. Certified, have a great evening!