Adding functionality to my Mopar/Jeep shop

Are the flourescent lights you are using the 4' T-12 lamps? Those are the fat 1 1/2" diameter lamps. Most of those ballasts have a minimum start temp of 50 degrees.

The 4' T-8 lamps are 1" in diameter and will fit in the same sockets and light fixture. Most T-8 ballasts have a zero degree start temp.

T-12 and T-8 ballasts are not interchangable.