Arrived at location on 1/27/22 - Lit pilot brought to 250 and it kept heating. Turned down to off before flames went out. Is off or on no control. Don’t have part on truck. Unit down requires part. Returned to location on 1/28/22 - Removed oil and old t stat. Replaced t stat with new one. Refilled tank and turned on set to 350. Unit reached 358 then burners shut off. And came back on at 345. Unit is operational job complete.