well i just got my fan harnest intalled on my 2001silverado an the may fan does not want to turn on!!!! does any body know if i have to get them tune so i can work????

 

Yes, you have to tune the truck for electric fans to come on. One fan works on high speed with the A/C if you plugged it in to the right green wire to trigger it.

 

yes that other fan turns on at the same time as the fan cluch does

 

gotta getta tune

 

There's a way around it I think. Lemme find the info.

on the nelsons 3 relay harness if your computer wont turn on fans,you can wire a switch to the blue wire that goes to terminal 42 0n pcm to ground.this will turn on both fans on low.and green wire that goes to ac wire can also be wired to a swicth to battery voltage and this will turn on one fan high.and if you have both switchs on,both fans go on high for good cooling.

 

That is correct, without the PCM tuned, you will either need a manual switch or one of those crappy probes that go into the radiator....