Hi! You may have purchased a bad DC-in...parts vendors are famous for selling parts "tested" without actually testing them, especially for items like DC-ins, which are not especially easy to test. I'd go back to the parts vendor and ask for a replacement.
It may be that your logic board was damaged in the rain as well, and it's causing the DC-in to self-destruct. I don't know how likely that is, but it's seems that there's a pretty good chance more was damaged by the rain than just the DC-in, and you may be looking at a bad logic board.
Also, DC-ins are weird little gizmos, and I've noticed that a "bad" DC-in sometimes behaves differently after it's been removed from a machine and allowed to discharge for a while. I've witnessed "bad" DC-ins working fine when connected to a different machine after having been removed and allowed to sit disconnected for a day or a week or whatever.
Anyway, what I'm suggesting here is that unless the original DC-in went up in flames like the second one, it may be worth re-connecting it to see if it's working now. Probably not, but it's worth a try. Also, leave the bottom casing and shielding off the machine, and you can test DC-ins without fully instaling them, simply by unplugging the old one, plugging in the new one, and leaving it dangling while you test it. That way, you don't have to do a serious amount of surgery on your machine until you know you've got a working DC-in.