DIY exhaust fan tripping GFI

I bought an off the shelf beefed up exhaust fan (one installed in a bathroom) and spliced it together with an old PC power cable. It worked great for sucking out all the smoke when I was smoking inside but when I took it out to my GFI circuited shed it was tripping every time. It is tripping the GFI, not the breaker, I know this for sure, I doubt very seriously if it is a short but I won't rule it out.

The fan is in it's little metal case and I used wire nuts and tape to splice. The only thing it might be is the fact that the PC power cable's wires were much smaller than the ones on the fan.

Any ideas?

One thing i found with my gfi reset switches is that anytime i introduce a new electrical draw it pops several times before getting used to it and not popping anymore.

Im guessing with the little knowledge that I know of electricity, your fan, on start up, is drawing a lot of current. The GFCI tripps because it thinks its a short. If it were me, I would make another outlet next to it that is not GFCI protected. make a jumper from the line terminals on the GFCI to your other regular outlet.

OR, if you know how your shed is wired, and there is another outlet that is GFCI protected, then switch the outlets. Depending on how your shed is wired, you may still have a GFCI protected shed, while having an outlet that bypasses it.

hope this helps.