Arrived at location on 6/27/22 - Disassembled unit and began inspection. Found heat relay filled half way with grease and no longer operable. Diverted 24 vac to ignition module to test function and got unit to lite. However unit does not want to stay lit and module throws an error right away. This is indicative of flame sensor failure. Ignition module appears to have signs of overheating at certain capacitors and relays. Dan said it was giving issues for a while before failure. Got permission from Dan to order all three items for repair. Unit out of service. Returned to location on 7/1/22 - Spoke to Dan. Disassembled unit and removed old ignition components. Installed new and tested unit. Unit fires up immediately and heats well. Back in service.