There's some great information on the forums. But sometimes they are wrong.
Other times the posts are correct for certain model year and engine combinations. Something that may be true in the past may not be true in the future. Take for example all of the threads on "how to adjust the TPS". TPS adjustment does not apply to the 96+ model year. But yet the forums are full of PPL saying to adjust the TPS to resolve idle issues.
As to which makes more sense to run the fan on HS or LS during AC operation, to me it makes more sense to run on LS. Why? Consider that if the fan were forced to HS, then there's no option/adjustment available should conditions not require HS operation.
Whereas if the fan runs on LS and cycles to HS when needed, this has the following advantages.
- Less noise
- Uses less power
- Too much air flow could cause the AC suction pressure to drop too low causing the AC to short cycle.
- Better control of the motor's temperature.
For further proof, a review of the Ford Factory wiring diagrams is needed. There are circuits that are specifically designed to force the fan into HS mode when the AC head pressure rises above a certain point. Why would Ford design in such an unnecessary circuit if the fan were already in HS mode?
If you are interested in seeing the wiring diagrams for yourself I may be able to help. PM if interested.
Finally. Consider that your car is over heating. By any measure you have already replaced a TON of parts with no solution. In cases like this, I usually advise people to stop and back up. Recheck your work. Finally see Occam's razor before starting to look for stranger/less likely possible causes.
http://en.wikipedia.org/wiki/Occam's_razor
I try to help people by as much as possible providing solid no BS technical advice (3,129+ posts). I often research using the Ford service manuals before responding. I'm going to drop off this thread as it seems that my input is not helping. Please be so kind as to update what the final solution is so that others can benefit from your experience.