My Electric Fan Project

[qcdstick]

I decided to do an electric fan conversion. I went out and bought at 16" fan and a thermostat control unit with thermal sensor. I also wanted to be able to control the fan manually from inside the car when desired, so I incorporated a 3 position switch (on, off, and automatic by coolant temp). Because having the switch accidentally left in the "off" position could cause the engine to overheat, I decided to also put in two LED indicator lights. The red one lights up whenever the switch is in the off position and the ignition is on. The green one illuminates whenever the fan is running. The switch allows me to turn the fan on even when the ignition is off, but when the switch is set to auto the fan only operates as needed when the ignition is on.

As the fan is 16" (high CFM) and the factory mechanical fan was 18" I chose to install the fan my mounting it to the cowl, rather than directly to the radiator as designed. I then filled in the gap between the edge of the fan and the cowl with some weatherstripping. This allows the fan to sit back away from the radiator and pull air across the whole radiator surface as designed. I used 8 bolts epoxied into the bolt receptacles on the fan and drilled through the cowl to mount the fan.
Note: I've since had problems with the weatherstripping coming loose at high speeds from vibration and or air pressure and am seeking alternative materials to fill the gap. It works without the weatherstripping, but it allows some of the air to flow around the fan rather than forcing it to pull through the radiator so there is not as much air pulled through the radiator as I'd like.



Pictures and diagrams!



Pictures of the fan mounting:





Fan installed (note weatherstripping now gone)


Location and clearance of electric fan vs the pulley where the stock mechanical one mounted:





I was not able to find a place to install a thermal sensor internal to the pressurized cooling system to take the temp directly. Also the fins on the radiator were too fine for the standard after market temp sensors to fit between radiator fins as designed. I decided to take the standard after market temperature sensor (silver part pictured in the link below this paragraph) and affix it to the outside of the hose flowing from the radiator to the engine. I took another piece of radiator hose (purchased at an auto parts store), slit it down the side, and wrapped it over the existing hose and the sensor to insulate the sensor to the temperature of the hose. A couple standard hose clamps hold everything together. It is an improvised solution, but after lots of testing (and 8 months) seems to work very reliably. I have the adjustment on the thermostat set so that the fan comes on just before the temp gauge in the dash starts to twitch above center, just when its needed and not before.


If you look closely at the top side of the added hose section you can see the wires leading to the temperature sensor.




Now for the wiring. Here is a rather crude diagram of the wiring schematic I used.

The only change is that the power to the left side of the switch is connected to a always on 12v source so that the fan can be turned on when the ignition is off.

Here was the resulting control box (standard temp control unit, red LED relay, fan control relay, plus the connections between them):




Here is the control box installed in the car, I located it in the dead space behind the driver's side headlight



Dimensions are 2.5"x2"x6" and it houses 3 relays and assorted connections. Ended up with no less than 13 wires coming out of it that need to be run various places... all to switch on and off a fan

The connecting wires are as follows:
Red LED + (light is on whenever the switch is in the off position)
Green LED + (comes on whenever the fan is working)
LED Ground
Ground in
Switched 12v power in
Switched 12v power out (to switch)
"ON" wire (from switch)
"Auto" wire (from switch)
Red LED control wire (from switch, to relay)
Fan Power in (25A fused, 14 gauge)
Fan Power out (14 gauge)
A/C wire (to turn on fan when A/C is on)
Thermal sensor




LED installation

I chose to mount the LEDs in that goofy place in the dash next to the fog light switch.



LEDs off (fan on auto but not running)



Green LED on (fan on either from temp or by manual switch)



Red LED on (switch in off position, fan will not turn on)





Switch installation

I chose to put it behind the garage door in the center console where it can be easily accessed, yet not easily bumped if the door is shut.







And finally, some pictures of the engine bay and the wires I ran. It could be a bit cleaner, but I don't tend to be too picky about the aesthetics of my engine bay.





I compiled this rather quickly, let me know if I forgot anything or if something does not make sense. Food just showed up at my door, so for now I eat!


Edit 10/30/2014:
Someone asked me about pictures for this thread, luckily I was still able to locate them since the old host is long gone. A couple additional comments - I ended up scrapping this fan/shroud combination due to not being able to keep the weather stripping between the fan and the shroud, which allowed air to circulate around the fan rather than through the radiator. I have since moved to a zionsville radiator, fan, and shroud which does a magnificent job. I have kept the wiring as it is described in this writeup, with the exception of moving the relays to underneath the passenger side air-box by the brake fluid reservoir for better weather protection. An additional change I made was to turn down the thermostat slightly, so that the fan kicks on sooner. I never had a problem before, but the temp gauge in the car isn't true, it will read dead center for a wider range of temperatures and does not start to move towards hot until things are already plenty warm. Therefore, waiting until you see the needle start to move before kicking on the fan is probably not the optimal strategy.

[Shardul]

awesome wirte up, does the engine rev up more freely?

[qcdstick]

I don't think anyone could tell the difference in how fast it revs. Technically, I'm sure it does rev more freely, but the resistance from a fan hooked to a 300hp motor any difference you perceive would probably be only in your head. Given that the fan never runs on the highway and rarely in town unless I'm stuck in traffic, I'm sure fuel economy and power both improved by some small amount vs the mechanical fan always running.

[fragzem]

Your red/green leds -- did you drill through there to install them, or you got that delete plate to come out? I wanted to put a switch there for something a while back and couldnt get that plate out.

[qcdstick]

Your red/green leds -- did you drill through there to install them, or you got that delete plate to come out? I wanted to put a switch there for something a while back and couldnt get that plate out.

The plate pops out, but you have to get your finger up behind it to do it. Its been a while since I did it, but I'm pretty sure you just pop off that piece of trim (the one with the cruise control button) and you can get a finger up behind there to release it. Maybe I had to undo some screws to loosen a panel, but I know I got to it from underneath. There is just a tab on the top and the bottom of that blank piece that holds in it, push up on the bottom tab and push it out. Then you can take it inside and measure/modify to your liking. IIRC there was a good bit of room behind the plate for stuff, the LEDs I used had the resistor already in them so they were rather deep. It's a great place to put LEDs or switches.

[AlMyPal39]

I've been watch the last few topics on electric fans. One guy with and M5 mentioned using and e36 temp switch drilled tapped and screwed into the t-stat house. Will not work on a 540 cuz of the eletronic t-stat doesn't have enough room.

There are three kit avaliable to trigger the electric fan. On my Suburban, I used and dual fan control kit that had a temp sensor that screwed into the cooling jacket. The turn on temp was fully adjustable and turne off after 20 degree drop. I HATE THE ONES WITH THE STUPID PROBES IN THE RADIATOR FIN OR PLACE ON THE RADIATOR HOSE.

I plan on doing a little more research on installing dual fans with this dual fan relay kit. I bought the kit for my Suburban 5 years ago in San Diego. I gotta see if they still sell the kit. I dont know what thread pattern the temp sensor has or what bushing adapter it came with.

I think there is a crossover cooling pipe in the back of the motor that has a thread plug in it already!!!!! That where I'm gonna install my temp sensor!!!

Check this out.. number 8 and 9
http://www.realoem.com/bmw/showparts...=11&fg=35&hl=2

[vien]

what does the temp sensor you used look like ? to get a better idea

[qcdstick]

It's on top of the box in this picture