LS1 Computer and Cooling Fan Question

[Phillip_L]

I posted last week that my car got hot because the fans quiet working.

Well, I found the problem and it is not pretty. Street and Performance build my entire harness and I had them add in relays to control the fans with the computer. I still do not completely understand what they did because they were using three relays to control two fans. Basically all three relays were receiving power from one 12 gauge wire and an even smaller ground. The 12 gauge power wire was discolored, splitting, and melted to the shrink wrap. The little ground wire was starting to do the same. When it went, it also melted part of the fuse box on the S&P harness and welded the fuse into the holder. I mention this so other with a S&P harness can beware.

Now to the real question: I am going to order a real harness for the fans from Ron Davis this morning. S&P was tying into two wires on the harness. What does each wire do? Is one a trigger from the A/C or are there two temperature settings in the computer (Hi/low) (two fans/one fan)?

[DJW32]

Hello Phillip,
Take a look at this
http://ls1tech.com/forums/showthread.php?t=472609&page=2
Go to post #27

I do not have the answer you are looking for but the link may help

[Phillip_L]

No, I need more of the pins out from the ECM?

What do the following Do:
Blue 42
Red 33
Red 17
Red 43

[Phillip_L]

Here is the link I was looking for:

http://ls1tech.com/forums/showthread.php?t=602292

It is a great picture.

Do anyone know what Red 17 and Red 43 does? I know it has to do with the A/C. Should I fire both fans when running the A/C?

[ggriffin59]

In my LS1 swap research, I found that one relay is controlled with "A/C on", the other controlled by temperature.
BTW, I haven't made a wiring harness purchasing decision yet, so thanks for the consumer report.
Griff

[jannes_z-28]

I posted last week that my car got hot because the fans quiet working.

Well, I found the problem and it is not pretty. Street and Performance build my entire harness and I had them add in relays to control the fans with the computer. I still do not completely understand what they did because they were using three relays to control two fans. Basically all three relays were receiving power from one 12 gauge wire and an even smaller ground. The 12 gauge power wire was discolored, splitting, and melted to the shrink wrap. The little ground wire was starting to do the same. When it went, it also melted part of the fuse box on the S&P harness and welded the fuse into the holder. I mention this so other with a S&P harness can beware.

Now to the real question: I am going to order a real harness for the fans from Ron Davis this morning. S&P was tying into two wires on the harness. What does each wire do? Is one a trigger from the A/C or are there two temperature settings in the computer (Hi/low) (two fans/one fan)?

You maybe have found the information already, the reason they put in three relays is that you have three steps in running the fans.
1. Using only one fan.
2. Running two fans at half speed.
3. Running two fans at full speed.

This is controlled by the computer depending on information it gets from the temp. sensor and the A/C status. In the computer you can set temps that activates low speed and highspeed.

If you use A/C you should let the computer knows what the A/C does. Then it will raise the idle when the A/C compressor goes on and also turn on the fans.

Use the same setup as GM has. It will require that you use the LS1 A/C pressure sensor in the system. If wired properly your computer will activate the A/C compressor and also turn it off when overloaded (to high pressure).

Ls1tech.com has all the info in the conversion section.


Jan