I seem to remember hearing about some way to use the PFC to control when the radiator fans come on, but I can't seem to find it anywhere. Am I remembering right? Also, if I can do this, will I still need my thermoswitch?

Thanks

 

You can essentially modify this older writeup:

http://rx7.voodoobox.net/howto/fanswitch/fanswitch.html

I'm reasonably sure that if you wanted the fans to all run at high speed when the car gets to temperature, you would splice the PFC output wire (in red below) to the other two relays (in blue below). That would eliminate the need for a thermoswitch completely, and would still allow the fans to turn on at low speed while the A/C is on and the car is not at operating temperature. Get a Datalogit and go to settings 3. Put all three fan settings to 87 C. Now the fans will come on at 86 C and turn off at 85 C as the car cools down. There are other ways you can do it. I have used a variation of this setup on an FD that had ditched the stock fans and gone with a single aftermarket one.

 

Is there any sort of drawback to having the fans always running at the high setting when they get activated?

 

From the perspective of a factory engineer putting together a bone stock car, there would be somewhat more current draw (not a big deal if your alternator is healthy) and more noise (not a big deal on a modded car), and the fans might cycle on and off a bit more. that's partially why there are multiple speeds to the fans from the factory. The Rx-8 uses the same multiple relay setup but it is more sophisticated. The fans still come on at kind of a high temperature on that car (just like the FD), but that is correctable by reflashing the ECU. The control logic on the '8 is all in the ECU and the ECU switches the relays on and off based on vehicle speed etc.

Getting back to the PFC: From what I have seen, running a Flex-a-lite Black Magic single 1 speed fan, the fan just stays on and the temperature stays at 86-87 C most of the time. Occasionally (cooler days mostly) it will drop down below 86 C (with PFC set to 87 C, fans come on at 86 and cut off at 85) during prolonged idle. It may go as low as 82-83 C for a minute, and then cycle back on. This is only if you are idling for prolonged periods of time.

 

Your profile says you have an FD. With the datalogit you just change the fan temps, no need for any wiring...

 

^+1, that's alot easier than wiring up a switch.

 

So I just the fan settings to 87 C?
Thanks guys. I thought I remembered there being a way that you could control the fans throught the PFC, I just wasn't sure if I still needed the thermoswitch.