Fan wiring help
Thread Starter
Launching!
Joined: Jun 2011
Posts: 244
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From: Walnut Creek, ca
Fan wiring help I need help with wiring my fans. Picture #1 is how the wiring is if I have a standard SBC. Picture #2 is how I think it should be wired now that I have a LS3/computer. Let me know what you guys thinn! thanks
TECH Apprentice
Joined: Jul 2011
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On mine I only have a single fan but its not done like that. Mine is done as follows.
The PCM is only completing the "ground" to the relay pin 85. Pin 86 gets 12v from the ignition being switched on. My fan doesn't run when I turn off the ignition but then again I really wouldn't want it to simply because of the drain on the battery. Pins 30, and 87 are the same as mine.
The PCM is only completing the "ground" to the relay pin 85. Pin 86 gets 12v from the ignition being switched on. My fan doesn't run when I turn off the ignition but then again I really wouldn't want it to simply because of the drain on the battery. Pins 30, and 87 are the same as mine.
Thread Starter
Launching!
Joined: Jun 2011
Posts: 244
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From: Walnut Creek, ca
On the paper from Speartech it says that the pink w/black wire is 12v key on to pin 85. the dark blue and dark green are ECM ground control to pin 86. That would be opposite from what you have described?
TECH Fanatic
Joined: Oct 2011
Posts: 1,356
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From: Felton Pa
I am using a '03 truck PCM and it has no fan control cucuit. I am going to use a universal thermostat with a probe that goes into the radiator fins to control the fans. They have a small screw to adjust the temp.
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On my Chevelle. I used a standalone system that is not linked or wired into the PCM. I used two SPAL fans and there standalone controller. I can set the two temp to come on for low and high speed on the fly. I was able to use the 99 temp sender on the driver side head to input into the SPAL PWM controller. Has worked well for over 5 years.
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Just another option.
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Verdad Gallardo TECH Apprentice
Joined: Jul 2011
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You are correct mine is 85 12v, 86 ground. It was late and I guess I wasn't thinking straight.
TECH Resident
Joined: May 2004
Posts: 792
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From: SoCal
I'm not familiar with the LS3 PCM switching, but by your scematic it looks the same as my LS1. The stock LS1 switching scheme runs two fans in series (so each fan sees 6V) for low speed, then switches to parallel (so each fan sees 12V) for high speed.
Andys
