2 LS2 Fan Questions

[JimmyJazz]

1. If I have a single large fan on my ls2 conversion how do I configure this in efi tune. I want to have simple on at suitable temp and if possible an overun if engine is turned off. A pic of the settings would be great

2. If I use two fans what are the settings to turn the first fan on at full speed, followed by the second. Again a pic would be great.

Hope that makes sense, just starting to get to grips with efi (can you tell)

[Mr. P.]

The fans don't physically work the way you describe. In the GM implementation, the fans are either "high speed", or "low speed" - either way they are *both* running. If you were to have only one fan running, then you would get NO airflow because there is a huge HOLE beside it! (because the other fan is off).

For a one-fan solution, you wire a relay to the "high fan control" lead on the PCM - when the PCM 'grounds' that wire, it turns your relay on and that powers the single fan. In the software, you type in the same temperature in both the Fan #1 (aka low-speed fan) and Fan #2 (high-speed fan) text boxes.

For a two-fan solution, you need to create a 3-relay control circuit similar to the GM design.

I have invented a low-profile EFan solution for the GM-800 series trucks ('99-'07) and sold about 50 sets; I sell the control box I describe for $135. Another vendor that can supply a cheaper/simpler relay setup alternative is Blackbear Performance. Or you can search the internet for the relay schematic and make your own.

Mr. P. :)

[Sleeping]

What about wiring a 2 speed fan instead of 2 fans on a 04 gto pcm with only a high-speed signal wire?

[JimmyJazz]

Thanks for the replies. I have the idea about the install now. I am just in need of how to alter the tables. My previous car had an LS1 which was simple as it said fan 1 on/off and fan 2 on/off. The LS2 table is totally different. I have attached pics of settings as they are now and hope you can point me down the right path.

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