[HotZ28]

If you could find someone with a scanner, it would help; but most likely, you have a PCM quad-driver fault. The engine coolant temperature (ECT) provides the PCM with engine temp readings and if the temp reaches a point to where the fans should come on, the PCM quad-driver will ground the fan relay(s) and the fan should run. The fact that yours does not run even with the AC on, confirms this theory.

Sounds like you need a new/rebuilt PCM, however in the short-term, you could mount a toggle switch under the dash to ground the fan relay(s) the same as your mechanic friend did when he tested the relay to make the fans run. One side of the switch will go to ground and the other side to the relay ground; flip the switch and your fans will run with ignition on.