I bought a set of factory E-fans from a local salvage yard and a wiring harness from Nelson performance. I swapped it onto my 2000 2500, which sits at my tuners shop. It is wired up according to their instructions, but the fans absolutely will not turn on when the AC clutch is not engaged. When the AC clutch is engaged, the fans operate normally and are activated by the ECM when the appropriate coolant temp is reached. Any ideas? Is my tuner overlooking something?

 

If he has HPTuners, he should be able to use the VCM controls function to turn them on manually. If they operate properly using the VCM controls, then a problem with wiring as an issue is eliminated. If they don't come on, then you can use that function as diagnostic tool to trace the wiring problem...

If he has EFILive, well, I have no idea if they have a similar function or not.