Here is the sentence:
Class with Dr. Rogers was a nightmare: the clock
seemed stuck in place, the air conditioner
blew inadequate cool, and a fluorescent
bulb buzzed overhead.
When you list grammatical items, you must use parallel structure. In this sentence, you have three short main clauses: the clock seemed stuck in place, the air conditioner blew inadequate cool, and a fluorescent bulb buzzed overhead. The list is thus parallel. Super choice!