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DYI: Mechanical Fan to Electric Fan Swap

245K views 467 replies 143 participants last post by  jasondotcom 
#1 ·
Let me just start off by saying I know this has been covered before, but no one has given a definitive answer, so I figured I'd make a thread for future reference.

I have an auto, and our cars come with a mechanical fan (engine driven) as well as an auxiliary fan to help with A/C and extra cooling power.

However, when I installed my supercharger, I had to remove the Aux fan to fit the intercooler. Because of that, the car would overheat when sitting at idle for too long, or if I ran the A/C (which wasn't even cold). I had to find a solution. I started looking at aftermarket fans, while also researching if I could swap an electric fan from a manual transmission E46.

I found a couple threads, but no real answers. I finally decided to PM the almighty and infinitely knowledgeable Mr. Nick G @ Technique Tuning, who informed me that it is a direct swap, and he performs this swap on his steptronic cars with no problems.

The mechanical fan and the aux fan have both been removed on my car, and replaced with a single OEM electric fan. So far so good. No wiring, no fitment issues, nada. Plops right in, plugs right in, and works.

Part # 17-11-7-561-757-M14
Cheapest place to buy: Pelican Parts - Click for direct link
Price: $253.00
Why?: Because a good aftermarket electric fan costs $150+. This is $100 more, and it's a direct plug-n-play.


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#59 ·
@EmFiftyFour: yes I have to shift. That's the only way to be competitive. Have a look what NASA TT is about. It's not a drag race.

The short answer is I have a secondary transmission cooler.

The long answer...

From Aug 2003 to April 2006, I tracked my car without a secondary transmission cooler. The only time I saw my transmission temp rise during this period was mainly during summer tracking months. Was the car driveable? Yes. Did it go to limp or un-driveable mode? No. I wrote up a bit on what happens to the transmission control program in my blog. So you can read more there. I have data that dates back to Aug 2003 including track and non-track events.

In April 2006 I installed a secondary transmission cooler. The need for it came because as I started to drive faster around the track, the engine and transmission got a little more beating and of course to deal with summer track events.

Since then and until now, the secondary transmission cooler is used depending on track configuration, ambient temp and number_of_shifts/lap ratio. Why so? Testing months (Dec, Jan, Feb) are usually quite cold here and I'd like to avoid a transmission running with less than desired fluid temperature.

That aside, there are several other reasons why your transmission temp will rise even if you have the aux + mech fans under non-track conditions:

1. Faulty transmission thermostat.
2. Faulty transmission heat exchanger.
3. Filthy/clogged up radiator fins.
4. Coolant leak.
5. Transmission fluid leak.
6. Faulty fans.
7. Faulty water pump.
8. Low coolant level.
9. etc...

So given a healthy cooling system to start, the electric fan mod will be fine for your occasional canyon carvings and highway vrooming.
 
#71 ·
Hey Kepeng,

I guess its safe to assume that the wiring that is existing takes care of the switch that is necessary to turn the fan on? Because if it never had the need to do it before, did it? Just wondering. I am glad it worked out for you. Did you remove then mech pulley from your car and then go with a shorter serpentine belt or does the water pump run off of that pulley?
 
#74 ·
You will Remove the Front Aux Fan and Plug it into that Plug :D

-TrippinBimmer
 
#77 · (Edited)
Rephase: You can leave the Aux and Mechanical Fan if you want or can upgrade to a Electrical Puller Fan Only (Behind the Radiator) and remove the Aux Electric Fan.

-Anthony@BimmerBrakes
 
#84 ·
There is 3 fans Ken....1 Aux, 1 Mechanical, and 1 A/C Blower(Fan).

-TrippinBimmer
 
#99 ·
I don't like humiliating people, I just have a low tolerance for people who lack common sense, reading ability, and general human functionality. You humiliated yourself by saying we have 3 fans, and then being incapable of reading post #1 because this thread is 5 pages long. That's like someone asking you to look at the cover of a book, and you saying you can't do it because it's 300 pages long...

That being said, you have your answer. See ya!


As an update for everyone else, I've put a couple thousand miles on the car (in the city), with just the electric fan, and I've yet to have an issue.
 
#109 ·
I am going to do the swap next week and what I came up with is that you only remove the mechanical fan and wire the new electric fan parallel to the aux fan ( just cut the wires and wire in). So what you gonna have is two electric fans working together.
 
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