How Green Was My Thumb? - S3-E17
Character mistake: When Johnny is filling the radiator on the squad, he pays close attention to not over fill. After Chet comes in and asks a question to Roy, the alarm goes off, Johnny closes the squad hood, without pulling the radiator cap on.
Answer: I believe you are speaking of the old man, Mr. Wilson. He's played by J. Pat O'Malley.
Bishop73
Correct, it was J. Pat O'Malley...he also played the grandfather with his grandson when their rocket exploded, and also played "Old Bill" in the episode with Ann Prentiss, where Gage saves the little girl from the burning tree house, and her mother falls in love with him.