Fans

[Jenkins]

Just got the car running and the fans want come on I think the ECM not sending the signal to the relays. And does your wire from your ECM act like a ground on your relay .not like wiring up a fuel pump relay thank on a 05 ls2 :attn:

[Chris 68]

I too have an LS2 (from a 2005 GTO) and just got my fans working recently. I'm using an ISIS setup so no relays for me, but the original setup is a 3 relay setup. I'm assuming you are using an E40 ECM. Yes the ECM will provide a ground signal to the relays. You should have 2 ground signal wires from the ECM. One will be a low speed signal and one will be a high speed signal. If you want the fans to run at high and low speeds you will need to wire the three relays so that when the low speed signal is grounded, the relays will power the fans in series. When the high speed signal is grounded, the relays will then power the fans in parallel. Here is the correct wiring diagram that illustrates this: http://ls1tech.com/forums/attachments/pcm-diagnostics-tuning/352229d1335928777-wiring-one-fan-off-stock-pcm-harness-cooling-fans.jpg

Hope that helps!

[Jenkins]

Thanks Chris it has a low speed wire and a high speed wire from the ECM and its is a e40 I would like to get it to work with two relays how does your work with no relays and is it still run through the ECM any help would be great I have tried everything

[Chris 68]

The only reason why I don't have to use relays is because I'm using an ISIS mulitplex system which basically replaces your entire traditional chassis wiring but don't get too caught up on that, I still use the ground signals from the ECM to trigger my fans. You can use two relays but that would eliminate your option to have two speeds for your fans. The simple way to do it would to just have one relay for each fan and ground both relays to the low speed fan signal from the ECM. Note that doing this would have the fans come on at full speed when that low speed ground is triggered by the ECM.

What have you tried so far?

[Jenkins]

Thanks Chris I did what you said with the low speed to both relays but they are not coming on till 205 I would like it to be at 160 thank for your help and now the idle comes up about 300 rpm

[Chris 68]

You can always have someone go in and adjust the settings in the ECM to kick the fans on earlier. I believe 205 is about the right temperature in the stock settings to kick the fans on. I sent my ECM and harness out a couple years ago when I was first installing the engine and I want to say I had my fan settings tweaked to come on earlier (around 180 ish) at least that's what I have seen on my temp gauge. Sitting in the garage at idle here in FL I see my temps sit around 190 ish. I'm no expert but from what I've seen from others, specifically in GTOs, your temps are normal. However I can't confidently comment on the idle RPMs though.

[TonyV]

Chris, i don't want to hijack the thread but i'm curious how you used ISIS without relays....i'm installing ISIS at the moment and i read that if you running fans you will need to use relays....

[Chris 68]

Well it depends on how many amps the fans are pulling and what you are using to activate the fans. I want to say this is true for most of the LS engines but I know for certain that on the LS2, atleast on the E40 ECM, the ECM provides a ground signal to fan relays. Since ISIS works on grounding inputs you simply tie the fan signal wires that would normally ground the fan relays and tie them into to the corresponding input wires in ISIS. On my particular set up I believe I had outputs 7 and 8 connected to my fans (each fan draws 20 amps) So output 7 controls one fan and output 8 controls the other. These outputs were chosen because they can be programmed to be PWM which allows you to very the speed of the fans in this particular case. So the way it works is one input on the master cell activates both fans at 50% and a separate input activates the fans at 100% so I tied in my low speed signal from the ECM to the 50% input and my high speed signal directly to the 100% on the master cell. Though I have to admit I'm still messing with the 50% function and have been talking to Jay Harris over at ISIS to figure out a solution (the fans are creating some back current when ran at 50%). So I've just been running the fans at a 100% when the low speed signal kicks on for time being (still works great!)

Hopefully that helps, feel free to ask whatever questions you have regarding ISIS and I'll be happy to share whatever I've learned. Also Jay is an awesome guy, and so are the rest of the people I've dealt with at ISIS, don't hesitate to give them a ring. They know their stuff and honestly the best customer service I've ever experienced whenever I deal with them.