I just replaced mine with a PM129 from autozone, it does blow harder than the old unit, how much I can't say but it feels stronger, and it's a single wire and a ground strap.. like the one on the right...
Where did you get the pmd extension harness?
Sounds like a loose or corroded connection somewhere to me..
What is under warranty, maybe let them handle it if they are going to dictate what you can and can't do...
If this only happens with the fan on you need another fan, at least it's the easiest and doesn't cost a lot, that would take the fan out of question...
So tell us what your search came up with, oh wait, ask FB and come back and tell us... And if you knew how to ask a real question you might have gotten a decent answer...