Arrived at location on 3/1/22 - Examined unit, customer said they smell gas and it's not heating properly. Found cooling vents and fans blocked with dust. Pulled burner cover and cleaned, pulled burner pack and cleaned flame rod and igniter. Reassembled and tested, could hear buzzing from gas solenoid valve. Failure is immenent for solenoid. Ran unit a bit and heard ignition module sparking to ground somewhere. Pulled right side cover and found module sparking to plate it sits on. Resistive spark wire attached, not necessary on this model. Reattached spark wire without and tested, found unit now sends spark to igniter like it should. Will quote customer to replace gas solenoid valve. Unit is working at this time.