Today preventative maintenance and heating checks were performed. Rooftop unit #49 had already had it’s heating functions disabled when I arrived. This unit has a heat exchanger that is breached. I tried to operate the heating functions and the unit did not start the ignition sequence. The other systems operated in heat mode. There are two belts that have worn into their pulleys and I do recommend replacing them along with retentioning the new belts. Rtu #48 has a blower wheel that is packed with dust. This unit is operating warmer than normal and I recommend removing the blower wheel to clean it. This will improve airflow through the unit. An estimate for the items discovered today will be provided. All three rooftop units were returned to A/C mode after the checks were completed. Thank you, Jon