Cody

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.

Project GatTagO

iTrader: (7)

The diagram says 2 speed fan, but you're talking about fan 1 and fan 2. Seems different.

Presumably the ECU has two setting for fan temps, a low point and then a higher setting.

Andrew

s14hunter

iTrader: (1)

^^^^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!

04Z06vette

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.

Andy1

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

Andy1

Cody

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.

Cody

Ok I wired it just like the diagrams that s14hunter and Andy1 showed. It works just like it is supposed to now. Thanks guys I appreciate the help.

s14hunter

iTrader: (1)

Awesome! Good to hear. Glad we could help ya out!

Cody

I appreciate the help. Now if I can get my trans to work right, I could actually drive it.