After installing the relays and fans will I need a tune on my 01 SCSB?

 

Yes, the fans will need to be activated in the Tune

 

A couple quick questions.

One, Pin 33 for the A/C is the Recirc Door signal. Is that right? Pin 17 is labeled A/C Request. That seems to make more sense to me.

Two, where are you guys getting your key on power from? Are you just tapping into an existing fuse? If so, which one seems to handle the load best?

Thanks guys, I think I'm gonna tackle this over the weekend.

 

The tune is changed so that its Fan #2 control instead of Rec Door Signal. Have no idea what Pin 17 does. Unless its from the HVAC controls to request AC.

If you remove the plastic cover over the fuse block, you will see two Studs. They are fused. pick one.

 

the way i see it, in the 3 relay neither fan is going to come on until the ac circuit is switch, the ground for fan one runs to the power of fan 2... idk

 

If you trigger relay 1 its gonna send power to fan 1, then thru relay 3, thru fan 2 then to ground. Giving each fan 6v which is half speed.

Trigger relay 2/3 and you get fan2 on high (12v).

Trigger relays 1/2/3 and both fans are on high (12v)

 

ok so who can help me with this then i did the i changed from the 3-pin relay to the 2-pin relay and now my a/c clutch compressor starts running as soon as the truck starts and the fan along with it. is there something different between the two that would cause it.

I grounded it to the battery and started it and it did the same, but when i took the ground off the battery while it was running it shut the fan off and the clutch compressor kept running.

oh and this killed my battery also.

 

Bringing this back from the dead with a quick question.

I have wired up my fans on a 2000 silverado according to a different diagram that looks just like the 3 relay diagram above with the exception of one thing. I have the A/C trigger wire tapped into the dark green wire (circuit 59, circled in red below). my passenger side fan is on constantly even with the key off ( have to disconnect the fan or battery to shut it off). I am pretty sure this is my problem.

I stumbled upon this thread and it says to tap into the green/white wire (circuit 459, circled in blue below). Looking at my harness it runs from the under hood fuse box down to the PCM. Is that the correct wire to tap into?

 

I think this will help you a lot, https://www.performancetrucks.net/fo...-truck-542739/

To answer your question directly, the fan itself is power activated, while the relay control is ground activated. The fan is always grounded even when off, thats why it activates your relay at all times.

 

So if I am reading your link correctly you wired up your fans according to your picture posted in the first post. Correct?

I didn't was not planning to switch to an 02 OS and wasn't planning on using an overide switch, but from reading that link it looks like if I don't I will only have low speed with the ECM and high only when a/c is on.

I am still confused on if I should be in the green/white wire. If I am thinking correctly it shouldn't make a difference.

If all else fails I will pull the harness back apart and wire it up as you had it along with the OS swap as it's not a huge deal.

Just want to get this thing done lol