I thought I had seen this part in one of the Acela exploded parts diagrams I have recently looked at. The only thing that is close is indeed the fan drive pin referred to above. The parts photo appears to show it with a slightly longer end but that doesn't necessarily mean it's not the same part that the factory used:
On all of the individual car parts lists I have seen (they seem to be pretty much identical apart from the body shells and interior assemblies) this is listed as part #11 and there are four of them used per car. They are related to parts 1 and 19, the AC housings and the fans inside them.
