I have a quick question for the guys that are running electric fans. I just received my new aluminum radiator along with dual 12 inch fans for my 82 CE. I have several questions.

The original wiring going to the factory fan I believe is black and blue and Installed a sensor that kicks in the fan at 185. Can somebody explain how this system works. From what I can remember when the sensor is either on our off. When is on it completes the ground and switches on the fan??? Do I use this system for the new fans or just install new relays and wiring for everything? The new fans are 12 inch draw 8 amps each and move 1250 CFM.

Mount them on the inside out outside of the engine compartment?

Push or Pull?

 

Push or pull depends on what side they're mounted.
The air should flow from the front of the car towards the back, just like when you're driving.

 

I would consider making a new circuit rather than trusting 30 year old wiring. Here's how I wired dual fans on my 460 Ranchero: Ran a 8 gauge wire from the battery to the power in side of a cole hersee constant duty marine type solenoid #24059 rated at 85 constant use. I ran a wire from the temp sensor to the ground terminal(one of the small studded terminals on the solenoid, does not matter which one) on the solenoid. Ran a "trigger" wire from an ignition on 12 volt source to the other small terminal on the solenoid. For the power out side of the solenoid I ran two 10 gauge wires through 2 circuit breakers, one wire to each fan. I also wired in a manual switch that will turn the fans on without the ignition on. The original owner had used a single plastic relay to run these big fans and fuses would blow and relays did not last that long. The 24059 is available from Amazon for $9 which is a bargain as some places want $30. Much more heavy duty than a plastic relay and easy to wire with 4 studded terminals.

 

The engine driven fan, with the thermostatic clutch, was the primary source of cooling; the electric fan was a 'added' fan which was intended to supplement the cooling capacity when the car was at idle for sustained periods (ie, traffic jams, etc.).

Any electric fan would be best on the backside of the radiator, where it would not block incoming airflow. If you have only electric fans, they should be fitted into a full-face radiator shroud where their efficiency would be maximized. Just hanging them on the back of the radiator would leave a lot of radiator area with no real airflow coming through it, without that shroud.

Contrary to what many folks believe, the electric fans DO NOT provide FREE cooling power. They absorb electric current, which must be produced by a larger alternator. The energy level of that electric current is about the same as the work-energy absorbed by the original mechanical fan, so there is no "free lunch". Thus, your alternator and the wiring from it need to be upgraded to handle that additional load, as well.

You can set up whatever fan actuating strategy you wish to use. The most energy efficient method would be to have one of the fans turn on at a prescribed temperature (ie, 190*F) and the second fan turn ON at 210*F and OFF at 205*F. That would allow you to only use one of the fans all of the time and two fans some of the time. There are controller boxes for dual fans that are programmable for just that purpose.

 

I bought "reversible" electric fans which could be wired as "pullers" or "pushers".

I found that the fans didn't cool as well and "ran more" when mounted on the front of the radiator and "pushed" the air through it.

When I put them on the back side of the radiator and reversed the wires (which required me to re-locate the radiator forward 2" on my '34 streetrod to have clearance for the E-fans) they ran much less in city traffic on hot days.

 

Electric fans are more efficient at pulling air than pushing and should always be used that way if possible. They are usually mounted in pushing mode when there is a issue of space for the fan and usually then as an axillary fan to help cooling in situations like traffic in high heat locations.

My 80 L82 had the auxiliary electric fan. The stock temp switch was so high you would have to be in a near overheat condition for it to come on. I didn't have cooling issues, so I never replaced the sensor/switch with a lower temp one.

 

the oem electric fan switch was set somewhere around 235 deg. I used the oem wiring, blue/black as power and ground for the 2 fan relays, triggered by temp switch.
http://www.jegs.com/i/JEGS+Performan...10570/10002/-1

 

You want them to pull if at all possible...

 

No surprise. The stock system pulls air through the radiator.

 

So it sound like I set them up to pull off the relays. So how does the blue / black wire and sensor work

 

Why do you say that? It probably depends on blade design. Except for the blade detail and maybe differences in shrouding, the fan in front has the advantage of pumping fewer cfm to equal the volume required by the rear mounted pump to do the same job of cooling the radiator.

langg

 

I powered up one if the fans black to neg and blue to pos. the fan looks like it's set out of the box to pull. Here is a pic of my new setup

 

I would use a Bosch style relay for each fan and wire them up according to the second diagram at this link.

http://www.aaroncake.net/rx-7/efaninstall.htm

I really don't know how the original wiring works, but you could also use the 2 wires from there (blue and black you believe) and connect them to the 85 and 86 terminals of the relay. Stick to the same wiring as shown for the 30 and 87 terminals.

As a third option, you can use 3 relays and 2 temperature sensors to wire the fans in a low-high speed configuration. This would put the fans on at a slower speed first and then step them up to full speed if they don't cool enough on low speed. Many newer GM vehicles use this wiring setup. It is quieter and less wear on the fans. It's more complex to wire though.



Yes, The only reason pulling works better is that the blades are designed for pulling. They have been compromised to be suitable for pulling. The same fan would cool better as a pusher if you reversed the blade design and pushed with it. Think how every computer CPU cooling fan pushes air over the heat sink. I work with industrial electronics and pushing with the fans always gives the best cooling.

 

Isn't it because computer components are mounted to something on the other side? You have no choice but to push if you're cooling a cpu/heat sink that is mounted to a system board. This is not the case with a radiator. Everything being equal, both pusher & puller designed blades are equally efficient but there are good reasons for using pullers on vehicle radiators ... one of them was mentioned above in a previous post.

 

Yes, the sucker electric shroud lets the grill air hit the whole front of the rad and sometimes there are rubber flaps in the shroud to let the air exit on the back side too. This wouldn't work as well in reverse.

But why does the heatsink configuration matter on a CPU? It'd be a simple matter to just change the blades so the fan sucked instead of blowing. If something is on the side opposite the fan then the air is just exiting the heat sink somewhere else (sides that are not opposite the fan). The air might not go straight but it still has to pass through the heat sink to cool it.

 

The heatsink attached to a CPU is the focus (engineered that way) for cooling the CPU. If it wasn't then there is no need for a heatsink, just blow cool air over the cpu ... we know that won't work with modern cpus running multiple cores and gigahertz speeds.

Also, pulling air past the CPU which heats the air slightly and then flowing it past the heatsink is counter productive ... hence pushers instead of pullers.

Back to radiators: I mentioned that there were good reasons for pulling vs pushing ... one being that the fan motors & brackets disrupt the air flow before the blades get a bite into them thus reducing the total flow. Other considerations: 1) mechanical fans were on that side of the radiator with the engineered space that accommodated that design so it was logical to use pullers to place all fan motors/brackets in the same space. 2) on a vette with A/C there is very little space if none at all to place pushers in front of the 2 cores (condenser & radiator) and still allow the hood to pivot open at the front.

Tradeoff: The fan motors get blasted with hot air so life expectancy is reduced with pullers and probably why a double fan puller setup is more prevalent because it allows you to limp home in case one motor dies. The tradeoff is reduced fan motor longevity vs a less efficient pusher design that results in an overheated and cracked engine block.

 

This makes no sense?

 

"Pushers" block incoming airflow...simple as that.

 

I starting to call B.S. on the push versus pull. A fan produces X amount of CFM. That CFM is what is passing through the fan. Assuming there is no loss around the shroud and seal of the fan, the same amount of air is going to pass through the fan and the radiator. The same thing goes for the "fan in the way", there would be minimal difference and that would be based on aerodynamics, the fan is still in the way regardless if it's on the front or the back, it's still blocking X amount of area.

This would be a good one for Mythbusters.

 

Well, you just don't understand fluid dynamics.