ticking and popping sound in radiator

Concerned Apartment Owner

Hi all, I have a through wall AC units with radiators supplied with steam on top. At times some of the radiators start making a cracking and ticking sound when the blower for the unit is forcing air across the radiator. At other times one side of the radiator is cool when the blowers are on. Curious to know what is causing this. I recently had all the steam traps discs replaced. Someone told me it may be that the steam is condensing in the radiator instead of at the steam trap. Thanks