Here's the "correct" way to wire your fans such that they both come on when the engine is hot. The "old" method doubles the load on the primary fan wiring and relay, and this tends to blow fuses and cause a fair bit of voltage drop. The only additional part you need is a SPDT automotive relay. RadioShack doesn't seem to have these anymore, but any auto parts store should. You can also get 'em here: http://www.parts-express.com/pe/show...number=330-073

The B/L wire which, you actually need to cut, should be done down near the fan itself. Reason for this is that wire goes to two places, and if you cut it prior to the junction just below the A/C relay, then the A/C will turn on every time the engine starts to overheat, which is bad. So, not knowing where that junction is in the factory harness, cut the Black / Blue wire close to the A/C fan. This is the only wire that will actually be cut- the others are just splices.

The Blue / Yellow wire will need to be spliced up near the A/C relay. I've also attached a drawing which shows where the A/C relay is under the hood.