1. How do the cooling fans know when to turn on?

2. Which is the ac fan and which is the cooling fan?

3. How can I make them both come on when the key is turned on?

Someone please help me....I know you guys have done this.

 

cut the green/white stripe (or just green) wires from the harness & ground them (and hope your alt. is in good enough shape to support them both running at the same time).

 

When you say green wire, where is it.

 

passenger side, fan switch between no. 6 and no. 8 spark plugs. the wire going to that switch controls the fans.

 

The switch in the passenger side cylinder head actually controls the secondary cooling fan in a dual fan setup. Depending on the year of the setup, it may be wired in parallel with a pressure switch in the A/C liquid line, which also turns the fan on when the liquid line pressure exceeds 232 psig. The primary fan in a TPI dual fan system is controlled solely by the ECM. Access the wires to be grounded near the fan relays, if you want the fans to run continuously when the ignition is turned on.

 

OK stupid question. Where are the fan relays located?

 

It's been along time since moving my relays but, I think both should be located on the pass side radiator support.

You'll know them by having a 12-14ga orange (or red in some cases),
a 12-14ga black/red stripe,
a 18ga tan/white stripe wire &
green/white stripe wire on the relay harness plug.

Regardless of which side, they should be somewhere on the radiator support. If you still can't locate them, trace the wires from the fans up to the relays.