Guys,
I have the 05 E-fan in my truck with the Nelson wiring harness. As it is wired the passenger side fan comes on high every time the A/C compressor locks. There have been posts about the voltage drop with this and the 105 amp alternator, which I am goinging to upgrade. Another I noticed yesterday on a long road trip and the first time I've used A/C for extended period is that the fan also comes on regardless of highway speed. There is no need for the fan to come on with air moving accross the condenser at highway speed.

I plan on putting a thermostat in the A/C condenser in series with the A/C lead. Allowing the fan to kick on only if the temperature is high enough. Does anyone know a source for such a thermostat. The kind that goes through a radiator like I've seen used with the aftermarket fan kits. Anybody know what temperature I should use to kick fan on and off for the A/C condenser?

 

If your pcm is tuned correctly he can get your fans to not operate above 40-45mph.

 

I have HP Tuners and know what setting you are referring to. The problem is the 03 PCM on trucks was not intended for use with dual electric fans. It only has one output to turn fans on. To compensate for this somewhat the wiring harnesses available have 3 relays that allow control of the fans independant of each other. PCM output on, both fans come on low speed, they do this by just throwing 6 volt to each fan. The fan for AC cycling gets its input from the 12v line to the AC compressor, so when the AC comes on just the one fan comes on high speed. Should the pcm output be on and the AC compresser come on both fans kick in high speed. The PCM output is what is controlled and does not come on above whatever speed I want. It will not control the second fan used for the AC condenser.