When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My LS cooling fans won't come on. I have a painless wiring harness and the ECM is set to the stock fan temp settings. I have let it go to 250 degrees (measured from my code reader) and neither fan will come on. The painless harness has a blue wire and a green wire designated for fan1 and fan2. I found a wiring diagram online and that is how I have it wired. Is this correct? What is the pink wire from terminal 86 to 87a for? I now have it hot wired with a switch so it won't overheat.
^^^^He is correct. If you're running two fans that are controlled by the GM PCM, then you would need the 3-relay setup below. You can buy the relays pre-wired from Painless and few different places. I wired my FAL 420 fans this way and it works great!
Last edited by s14hunter; Feb 23, 2017 at 11:08 AM.
GatTag0 is correct. that schematic is to wire up a DUAL SPEED fan such as the Ford Taurus fan. When the HIGH speed kicks in, the pink wire removes power from the first relay. This prevents power from being applied to both wires of the fan at the same time.
so need a diagram for dual fans. I used this one which uses dual fans and also dual speeds.
One relay switches the fans between series (low speed) and parallel (high speed) configuration
- One relay provides power (half-current due to series operation) to both fans in low-speed mode, and just fan1 in high-speed mode
- One relay provides power to just fan2 high-speed mode.
The high speed signal from the PCM controls both the series and fan2 relay. The low speed signal controls just the fan1 relay. For both fans to spin in high speed mode, both signals are needed.
^^^^He is correct. If you're running two fans that are controlled by the GM PCM, then you would need the 3-relay setup below. You can buy the relays pre-wired from Painless and few different places. I wired my FAL 420 fans this way and it works great!
I used this schematic to wire up my fans for PCM control (Fbody). Relays switch fan circuit as follows: series = low speed; parallel = high speed
Thanks guys. I will try that. I had to send my ECM back to the tuner today to fix a transmission issue. When I get it back I'll let you guys know what happened with the fans.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
Need help with cooling fans please. 
