I was going to go out and get a villager e fan or taurus e fan whichever one I can find localluy. My question is when should an e fan be on? I was going to hook it up to a switch so that is why I am asking.

 

When you are idling.

 

Unless you're willing to wire the fan properly, you're much better off with a mechanical unit.

Here's why...
No one disputes that the OEM fan pulls a metric buttload of air and the shroud is very efficient. It's real weak point is the crude control method.
The advantage of the efan is the more direct and precise application and the method you propose fails in this regard.
If this is a street car, manually controlling the fan- which means constant monitoring of temp (you do have an accurate water temp gauge, right?) and remembering the switch- is just too much work and responsibility.

This is how I did it eight years ago (and on several cars since) and it's a simple and very reliable solution.

Based on 150k miles of use, I've reached a few conclusions...
-Before you consider the fan, consider the radiator.
You need a good one and you also want one with side rather than top/bottom, tanks...because the Taurus/Lincoln/etc fan shrouds fit that config better.

-Setting the low speed trigger temp at 195° works fine and saves a lot of wear and tear on the fan and less alternator drag. There is no point struggling to maintain the mythical 180° ideal when the thermostat isn't even fully open at that temp. If you let the thermostat fully open and your more efficient rad do it's thing, you'll be surprised how little the fan is used.

To directly address your question...the fan is never on at sustained cruise over 35-40mph.
In traffic, I'd estimate the fan is on maybe ten percent of the time but that's obviously highly variable.

Over the years, most of the efan "reliability" problems we've seen are directly attributable to crappy installs...either do it right or don't bother.

 

Thank you. I am going Koyo with the e fan. I wanted to hook it up to the Microtech lt9c but I do not have the adapter yet to hook it up to a laptop and change the settings (bought the car with it installed and running). I believe you can use one of the aux inputs to do so on the Microtech. I was just going to use a switch in the meantime.

 

What clokker said. Do it right and you don't have to think about it for the most part.

I f you just need something cheap until you get the microtech setup you could use this. https://www.summitracing.com/parts/hda-3653 and a relay from Autozone. I've used this setup along with a fuse for the fan for 16 years or so now with the sensor stuck in the radiator core just under the upper radiator hose.

 

IF you use a Switch that YOU have to turn on..that my friend will bite you in the ***!
Trust me,It wasn't long before I turned my "Fan on/Fan off switch" setup to a Thermo-activated system.
I had a hot start and turned the fan off to allow more juice to the starter..WELL when I got it going I forgot to turn the switch back on and drove away.
I was Damned Lucky when I saw the Temp gauge hit over 200!

and By the way: https://www.rx7club.com/2nd-generati...ed-fan-839089/

 

I have just installed an E-fan not to long ago. I see some people saying the fan should not be on when you are moving. How the heck do you have your fan turn off when you start moving?

I have mine wired up when it gets over a certain temperature it comes on. I have it stay on for the most part after this. Unless the car is just idling it is not going to cool way down. My cars temperature runs in the 180-190's for the most part.

Also how does the efan puller running hurt when car is moving?

 

We weren't so lucky........kept it off to get a little warmth in the car on a cold start...got distracted....bye bye coolant seals.

 

Some modern cars have a pretty sophisticated fan control system that changes with vehicle speed, grill shutters, etc.

For an old car like this, where fuel economy and noise and all that aren't a big concern, your control system is fine.

 

You install a wheel speed sensor or pitot tube and set the fan to turn on when the vehicle speed falls below a certain value. Some people also use a thermal sensor in-line so that the fan doesn't run when the engine is cold, and/or so it does run when the engine is hot but the ignition is off. If the car has AC then setting the fan is more complicated.

The moving fan blades create a "disk" that acts as a restriction to ram air when the vehicle is moving at very high speeds. When the blades are moving slowly or stopped then the ram air can easily swirl through them. This really isn't a factor for a street car though.

 

In a street car, the main objection to the "always ON" fan is that it's uselessly inefficient.
Why throw away electricity that costs you horsepower to produce?

The whole point of the efan is its precise control, if you just leave it on all the time, you've done nothing.

 

really easy to wire the e-fan, i'm using the villager one... aaroncake.net has the instructions. bought a little temperature control switch from a local electronics shop for like 15€, attached it near the rad intake with zip ties and a little thermal paste between the switch and rad... worked fine..
But now the ecu controls the fan.