Best Practices on Wiring a Transmission Cooler Fan?

matreyia

Major
Apr 19, 2017
1,751
690
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335i e93
Hi Everyone,

I would like to ask if any of you know the best practice of wiring an auxiliary cooling fan in the fog light area. Can we just use the positive lead in the engine compartment and integrate that lead with the aftermarket thermostat and resistors which come with the fan?

Or should we always take time and effort to literally make a new connection inside the fuse box and do god knows what to where in order to avoid electrical gremlins down the road after install?

I have the thermostat that fits directly into the Vader Solutions ATF cooler fittings, and a resistor switch and a 7 inch fan that I need to add for cheap insurance on the ATF temps.

Thanks in advance for your thoughts.

VT
 

matreyia

Major
Apr 19, 2017
1,751
690
0
Ride
335i e93

Often times, a general EE is not equipped to answer specific BMW best practices questions. I don't know if this is one of those times. For example, one would think that buying a battery from Walmart to replace the stock battery would be straight forward...until one realizes that it must meet certain criteria and must be digitally coded/registered to the specific car...and that it is not recommended to piggy back additional power lines directly from the battery terminals where the stupid complicated looking harness resides. Doing this supposedly gives rise to enough voltage variation that inexplicable electrical gremlins begin to rear their ugly heads.

VT
 

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700 HP Club (N54)
Oct 19, 2016
534
404
25
NY & AZ
vadersolution.com
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N54 135i & N54 335i
i made a limited amount of trans cooler harnesses that were PnP... time consuming and not really worth it financially ... i wont advertise it but i can do it for anyone just takes time
 

Kenjermen

900 HP Club (N54)
Nov 6, 2016
259
78
35
N las vegas NV
Your fine just taping into the dog light switch for power. I ran mine like this for awhile with no issues. If you want to give yourself warm fuzzies you can install a inline fuse and call it a day. I ran a switch for the fan inside the car.
 
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matreyia

Major
Apr 19, 2017
1,751
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335i e93
I prefer using the main power constant line, then the thermostat wire to the thermostat, then the negative to ground,...for the life of me, it appears NOBODY knows where to find the ignition wire in the engine compartment, or any accessory wire, or remote wire anywhere. I been looking for two weeks daily.
Found some vague tales of a Green wire in the CAS...until you look there, and you see multiple green wires - then you know, don't fool around there if it's not definite.

So I am at a loss.