Arrived onsite to inspected units for fall maintenance. Inspected all units in heat test mode verified proper order of operations. Documented all unit info and amp draws. Documented all findings. Found Unit #2 to have bad heat exchanger that is cracked and needs replacement. This Unit also has deteriorated heat rollout switch. Unit is shut down until Parts are replaced waiting qoute Unit #3 to have combustion motor with burnt wires needs replacement. This unit is still operational. Took picture and documented all findings 2 quotes