If vent motor runs all the time even with system on a/c. Could be stuck relay on control board. I have seen this happen. Had to replace control board
Unfortunately, that's a problem with modern equipment. They're using less and less discrete components. Gear chipped in window regulator for car? You've got to buy the entire window regulator including motor for $300.
If you know exactly which relay it is, you could rebuild the board though. The foot print doesn't have to match as long as the coil voltage and contact configuration and ratings meets or exceeds the existing relay.