I have an older Night & Day outside a/c condenser unit. The fan motor stopped running. The fan motor was a replacement, I replaced years ago from a spare unit. All the specs have been washed away by time. I replaced the fan motor with a 1/4 hp, 1625 rpm and new 5 uf capacitor. The new fan motor shuts off after 20-30 minutes, thermal protection. The house cools during that period, but at overheat, I shut the unit down to protect the condenser. My question is why am I overheating the fan motor? Should I have a lower hp motor and less rpm, or lower the capacitor? Night & Day model is 38DNR-108K, no manual or specs available. New motor was a grainger Item #3RCR7.

Good chance the motor you replaced it with has gone bad or wrong for the system. The 1625rpm is not looking right(to me). Do you know what the tonage is of the system? Model# off the furnace or evaporator coil will help. Make sure the rotation of the condeser fan blade is going the right direction... on some older Payne air conditioners(Day&night). The condenser fan would run backwards when the run capacitor went bad.