How to change my tune from Dual Fans to 1 single, 99 LS1 ECU

[ryeguy2006a]

Hi there,

I searched for a while last night and today and can't seem to find an answer to my question. I thought it would be fairly straight forward, but for some reason it doesn't seem to be something I can find searching. I have a 1968 Camaro that I'm running a LS6 cam only 5.3 and running a modified tune with a 99 LS1 computer. Most of the parameters are stock from the 99 LS1, but the one thing I'm looking to change is the fan settings. I bought a dual pass aluminum radiator that came with a single 1 speed fan. What I would like to do is simply hook up the one fan right now and am unsure how to accomplish this? Can I simply change the drop down menu in the fan section from 2 fans to AUX? I couldn't figure out what the AUX meant exactly. I currently don't have A/C, but I do plan to in the future, so I would need to have something to trigger the fans to kick on too.

Can anyone point me in the right direction?

Thanks,
Ryan

[2xLS1]

Depends on what fan wiring harness you are currently using.

[ryeguy2006a]

Hi there,

Thanks for the reply, but I'm not entirely certain what you mean? I currently don't have the fans hooked up, but was planning on using a typical 4 or 5 pin relay. I was also considering using maybe a 4 and 5 pin relay in conjunction with the A/C activation in the scenario where the fans weren't on but the A/C was on. Is that what you are asking?

Thanks,
Ryan

[wildkard]

Go to the system>fans tab, set the drop down for fan type to aux fans, and set the fan 1 on off temp to the speeds you want them at.

As for wiring with the AC if you run a trinary switch instead of a binary, you can get away with a single relay since you can have the trinary send a ground to trigger the relay just like PCM does. If you want to use just the binary switch then you will need a second relay to reverse the +12v signal that used to trigger the compressor clutch.

[2xLS1]

Hi there,

Thanks for the reply, but I'm not entirely certain what you mean? I currently don't have the fans hooked up, but was planning on using a typical 4 or 5 pin relay. I was also considering using maybe a 4 and 5 pin relay in conjunction with the A/C activation in the scenario where the fans weren't on but the A/C was on. Is that what you are asking?

Thanks,
Ryan

Since this is in a 68 Camaro I'm assuming you are either using a modified stock GM harness or an aftermarket. Both would usually have the fan wiring incorporated it them with 3 relays controlling 2 fans where they either both run low speed or both run high speed. That's why they use 3 relays to either configure them in either a parallel circuit or series circuit. If you don't have any fan wiring then just wire in a single relay control to the fan 1 PCM trigger output and set the temps for fan 1 accordingly. Make sure the relay can handle the current draw of the fan and fuse the circuit accordingly. You can wire in a 2nd relay triggered off the A/C compressor to turn the fan on with A/C.

[ryeguy2006a]

Thanks for the responses. Yes, I am using a modified 02 truck harness that I re-pinned to match the LS1 ECU. I currently have the two high/low trigger wires coming from the ECU to trigger the fans. They are un-terminated and waiting for me to make up my mind. I recently did when I bought the dual pass LS swap radiator with single fan. I was planning on running a 40 amp relay to trigger the large single fan. I will likely use the trinary switch when I convert to VA at some point in the future.

So is it safe to assume that the AUX from the drop down is what you would use when swapping to a single fan?