Yes the fans are controlled by two sources. 1) The high pressure switch on the A/C system and 2)the coolant temperature switch. If the pressure in the A/C system reaches a set level, both fans will come on at low speed. If the engine coolant temperature reaches (I think)approximately 110c the fans will go into high speed. There are two relays that control the high amperage flow to the fans though a resistor mounted near the fans. The resistor provides the path for low speed and is bypassed for high speed. The relays have fuses plugged into the top of them. The low speed relay fuse (15amp) is prone to easy blowing. I've replaced mine with a 20amp and haven't blown one in over a year. It is not a danger to that circuit to increase the fuse it a 20amp.
[Edited by ARJAY on 05-12-2001 at 09:07 PM]