Can't find a good ground?

Ok ok, I know this sounds funny...
I've literally tried about 10 different places on my MJ (I'm installing a Taurus fan) and CANNOT find a good ground!
I even went directly to the unibody, ground down to bare metal and everything, nothing! The fan works.... It's new.

Should I ground directly to the block?
Never had this happen before... I'm stumped.

are you sure the hot wire or 12volts + is good too?

if all else fails you can get away with putting it to the negative, but ive found that this kills the battery much quicker, and is kind of frowned upon. i ground all my things to the wall of the engine bay. its always worked for me...

I used the 10mm bolt on the top of the readiator support as a ground for my lights and has worked well for 2+ years.

I have my fan into the factory harness and have tapped where the relay goes to wire to the toggle switch.