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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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#112 ·
I do understand that. I gave just one more alternative
 
#114 ·
Well the problem that I had was that something went wrong with my car's ECU, and the electric fan it came out with never received a pulse to switch on when needed, resulting in a blown headgasket and cracked head :bawling: Now the cost of repairing that was rediculous, so I had the autoelectrician just make the fan run with a relay, so it's on all the time on full speed.

I can tell you, that noise was killing me. Last week I had it ripped out and replaced with a clutch fan. That's me, happy :)
 
#115 ·
Did the swap on my 328 AT. The result is amazing. I finally got rid off this bloody noise coming out of mech fan and the car became much more responsive and a joy to drive. So far no overheating issues ( it is 110 F here). I tried iddling with and without the AC for 30 min each. No issues. The temp gauge niddle at 12'o clock postion at all times.

Thanks kpeng.
 
#121 ·
going to do the cooling system soon... so this is a good time to remove the clutch fan and toss it. sounds way too simple not to do. Ken, I have a normal "non noob" question (sure you can appreciate that lol) When you installed the fan as a puller behind the radiator... did you utilize the stock fan shroud? and did it have to be modified in anyway(the fan shroud)?
 
#131 ·
Does this apply to M52TUs as well? because I've been reading a lot about the swap and am almost ready to do it, but I'm just held back by this:
Everyone that I've read about had M54s, and everybody still think manuals ALWAYS come with an electric. THIS IS WRONG!
Early manual E46 models have, like mine, a mechanical puller + an electric pusher.
My questions are: when did BMW throw away the dual fan system on manual cars? Is the swap really safe for manual M52TUs? Will a M54 electric fan work?
 
#132 ·
Does this apply to M52TUs as well? because I've been reading a lot about the swap and am almost ready to do it, but I'm just held back by this:
Everyone that I've read about had M54s, and everybody still think manuals ALWAYS come with an electric. THIS IS WRONG!
Early manual E46 models have, like mine, a mechanical puller + an electric pusher.
My questions are: when did BMW throw away the dual fan system on manual cars? Is the swap really safe for manual M52TUs? Will a M54 electric fan work?
I've done it on my SC'ed M52TUB25

The pusher fan was removed to make room for the intercooler , and the mechanical blew to bits a couple thousand miles ago.

Had the car overheat during rush hour and finaly got an electric one , the one i got though was either improperly wired or was supposed to push air from the engine through the radiator(wtf?)

So i switched the fan's positive/negative and now it works like a charm , can leave the car idling for 20min or drive through 10mph traffic the needle won't move :D
 
#134 ·
That's an interesting question ... do you have to remove the pusher fan from in front of the radiator? Replacing the mechanical fan with an electric fan, should be moving the AUC module from mech. shroud to elec. shroud, and plugging the large multiwire plug into the plug that powers the fan. Can both electric fans remain in place and both be functional?
 
#137 ·
I like the idea of one single fan - makes sense to me. Also, I am thinking of upgrading to a better aluminum radiator and running a separate trans cooler.
Then, I get the best of all worlds, while providing more protection to the auto trans. In Vegas, anything to keep the motor cool is a plus.
 
#140 · (Edited)
So, I'm sure I'm over-thinking this, but found it interesting. Using the diagram below which shows the auto transmission cooling setup... Note that the coolant which is routed to the auto transmission heat exchanger includes the the heated coolant from the engine along with the coolant exiting the heater. That means the transmission fluid has to be hotter than the mixture coming from the engine in order to cool the transmission. So, with hot coolant cooling the transmission fluid, I wonder why BMW continued to use a fan/clutch on automatics?
 

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#147 ·
First of all: Ken, thanks for the write up. I'm a noob, transitioning from the VW/TDI and Subaru world, into an E46. Clear and detailed write-ups like this, are priceless additions to all the DIYs/Maintenance threads.

Regarding the observation made by Sansho on the coolant, I found this excerpt from a training manual:


The training manual came from this thread (courtesy of shanneba):http://forum.e46fanatics.com/showthread.php?t=813901

or, click on "Automatic Transmissions" at this link: http://www.bmwtech.ru/
 
#150 · (Edited)
i have a question.....

I was able to find a free electric fan....however the module is blown....

My question is....can i swap the control modules from my a/c fan to the electric fan?
You can indeed do this , however the wires going to the fan will need to be reversed , else you'll suck air from the engine and push through the rad.
Also the connector from the module might not be long enough to sit in th plastic cowl(just stripe it down?)

The module has 3 inputs , +12v GND and a trigger.
The ECU sends a OSCILATING trigger to the fan control module which then gives +12v to the fan.
GND to fan is always on.

What you need to do is pry the holding tabs on the fan control module open and loosen the wire(dunno if bmw glue this or something but mine just came loose) then reverse the wire with the other side and close the tabs.
 
#142 ·
Like Jake inquired earlier in this thread I am also interested in keeping BOTH the pusher and the new electric fan operational. Does anyone have any ideas on how to make this work?

Also, it wasnt mentioned whether the thermostat for the aux fan functions the SAME or IS THE SAME as the thermostat for the elec fan on Manual cars. i.e. does the aux fan's themo monitor tranny fluid or coolant and does it cut in at the same temp?
 
#143 · (Edited)
There is no reason to have both fans involved. I recently came from a Trailblazer SS with an LS2 motor. One of the 1st things I did was replace the mechanical fan with an e-fan. If you do any research, you will find that transmission was very susceptible to overheating and failure. After almost 100K miles, I had no cooling issues at all. What was even better was that we did a dyno pull before and after the swap and I gained 10 RWHP just replacing the m-fan with an e-fan. I'm looking forward to investigating this swap further. It seems too easy on the E46 since I had to tune the TB for this application. The end result was that I was pushing 350 HP and 350 lbs of torque. E-fan will work just fine!
http://www.bmwpartsweb.com/BMW-Part...ept-M3-(only-if-equipped)__17117561757-BOSCH-
 
#148 ·
Also, it wasnt mentioned whether the thermostat for the aux fan functions the SAME or IS THE SAME as the thermostat for the elec fan on Manual cars. i.e. does the aux fan's themo monitor tranny fluid or coolant and does it cut in at the same temp?
The cooling management system assumes that there is one electrical fan, whether a pusher fan on an automatic or a puller fan on a manual transmission. It uses several inputs to decide when to turn the fan on, including the coolant temp (lower radiator hose sensor), calculated catalyst temp, speed, battery voltage, and calc'd a/c pressure.

That's why the electrical conversion to a mechanical fan is so quick ... you're disconnecting the front pusher fan connector and plugging in the new puller fan. All cooling management functions remain the same.
 
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