Originally Posted by paintballdude05
I'm thinking that your problem lies in one of the little known differences in cars with 2.7 vs 3.5 engines. The 3.5l engines have dual speed fans controlled by the PCM depending on a few variables. The 2.7l cars on the other hand mostly came with single speed fans so they were either on or off.
You sure about that Steph? That would have to be in the PCM programming if true, because the wiring, though different, gives both setups two speed capability - low speed with the lo-speed relay energized, hi speed with both energized.
There is one difference with the later year non-2.7 fan assemblies - the way they are wired would allow the passenger side fan to be run by itself at hi speed if lo-speed relay off and hi speed relay energized. I've never had it confirmed if the PCM takes advantage of that capability - again, the PCM firmware would determine that.
So the special PCM could be sending some "slow signals" to the fans yet they can only run one speed...
If the FSM schematics are right (and I think they are), that isn't correct. The 2.7 fan motors (and also 3.2/3.5 fans on earlier years) each have two windings. Lo speed is one winding powered. Hi speed is both windings powered in parallel.
The other fans achieve lo and hi speed with one winding on each motor. Lo speed is both windings in series (essentially 1/2 system voltage to each motor), hi speed is both windings in parallel (made possible by the two additional relays in the fan assembly)..