Additional radiant heater diagnostic added by Jeff upon arrival. Per weekend staff, system was only lighting halfway and excessive gas odors could be smelled in the SE loading dock area. Gas and thermostat was turned off upon arrival today. Visual inspection appears normal with no maintenance. Initial testing discovered a failure to ignite and relight on the first test. Subsequent testing discovered spark ignition system continuing to spark after heater was lit. System appears to be running normal otherwise. Remove spark and flame sensor electrode for resurfacing. High pressure air dusting of honeycomb heat exchanger and gas burner jets RTU number 10 locked out on service code for thermal cutout, TCO1 or TCO2 Air filters clogged solid and 100% matted over. Fan belt normal, heat exchanger inspection, all normal. Automatic reset 140 - 30 heat exchanger thermal limit will not reset and need replaced Part is not in stock in Columbus and will require one to two days for shipment Sys