Electric fans

[Chevy366]

Man got a problem that I hope someone can help me with here , I bought a set of fans off E-bay , it came with a harness from Nelson Performance , I hooked up the harness as per pics and instructions but the fans do not operate as they should , with A/C on only one fan runs (driver side) and with A/C off both fans run but at a very slow speed , so what did I do wrong ? I was a little confused on which wire to connect to in the wiring loom , it said solid green wire but their are two green wires one is a dark green and the other is a light green , I connected to the dark green wire, I used a ohm meter to test the connection and have 12v at the connection when A/C is on and 0.0 when off. I tested both fans and they both work when 12v is supplied to either one , I had pin 42 activated and am connected to that with the PCM.
Anyone got any ideas.

[RedHeartbeat]

If i remember correctly, all the wires going to the PCM from the relays are ground wires. If you give them 12v you wont be accomplishing anything. In the last couple of days someone posted the installation instructions for a Nelson fan harness. You'll find it easily with a search. There are two wires that run the fans, one is Red connector dark blue wire pin 33 and the other is on the blue connector dark green wire pin 42. Your PCM MUST! be setup to turn the fans on also on the Silverados. LS1 engines already use this function and are already set up to turn the fans on.

[Chevy366]

Thanks for the reply, BUT , as u could see I am the one who posted the diagram in the first place and I followed it to the letter except for the solid green wire thing. The wire I am talking about is not from the PCM it is from the loom coming from the engine block not the PCM , PCM is straight forward in that u have to disassemble the connector to access the pin 42 , did not see anything about pin 33 in the instructions . As u said the PCM does act as ground .
If Allen see this post I would greatly welcome his wisdom on this .

[jethro_3]

Mine ran as follows:

No A/C signal, temp signal on >> 2 fans on low

A/C signal on, no temp signal >> 1 fan on high

A/C signal on and temp signal on >> 2 fans on high

no A/C and no temp signal >> of course no fans on

Is this what you where looking for???

[Chevy366]

Thanks jethro_3 that helps , but I did somemore testing and found that one of the relays was not working , switched relay positions and voltage drop followed relay from socket to socket . Replaced relay with new one and got two fans when A/C was truned on but sence I still have stock fan on motor and just checking harness before commiting to electric fan , can´t get fans to turn on with no A/C , temp may not be high enough, but at least I know the fans work with A/C on. But I still not getting what jethro_3 says his did ?

[Chevy366]

Just one more quick question and I will put this madness to rest , at what temp does pin 42 from the PCM send a signal to the relay? Or is this set when the PCM is flashed and the tuner sets it at that time to what ever he wants to ?

[RedHeartbeat]

edzackery. The PCM can be set to any temp you like. You'd have to ask Allen what temp he set it to if you want to know. That or anyone with any LSx PCM programming software can download your file to their software and tell you what it is set at.

[jethro_3]

Those conditions where from the Nelson tuned PCM with Nelson harness on my '01 Pewter Sportside Silverado. The temp was set at 185, below 185 0 volts, 185 and above got 12 volts from the PCM.

[Chevy366]

Thanks all , for the info