Using the AC compressor wiring for electric fan conversion?

[m3f_hufflepuff_e935609de1]

DISCLAIMER: Perform this modification at your own risk. I am not responsible for any consequences.



For folks who have deleted their A/C system and would like to convert from belt driven mechanical fan to electrical fan, there is a very simple way to do it:



1. Get a 16" electric cooling fan; i got mine from ebay.

2. Attach the fan to the radiator using the OEM shroud (easiest, and retains factory overflow reservoir)

3. Keep the kep out of the ignition. Cut off the factory AC condenser connector (3-pin).

4. Wire the ground of the AC harness to the ground of your new cooling fan. i used a female blade crimp connector which plugs right into the fan connector

5. To wire up for two speeds, you will need to wire the low speed and high speed AC harness wires according to the following diagram:



http://i109.photobucket.com/albums/n43/mchuffman/M3fanwiring.jpg



Again, i used a female blade crimp connector to parallel the high and low speed wires to the fan positive. you need to use a high wattage resistor or it may get hot and burn up or cause an electrical fire. i used two 50 watt, 1-ohm resistors wired in parallel to get the neccessary power capability.



This setup uses the factory AC fan temperature switch, which will activate on low at 91C and high at 99C for a 96-99 M3.



To test operation, you can jumper the harness side of the temperature switch in the side of the radiator. following a wiring diagram for your year, jumper the low and high terminals to ground. With the ignition "ON", the fan should run in low and high speeds.



There you have it, aftermarket fan is wired up without using relays or additional temperature switches.





ORIGINAL POST:



Hi all,



I'm looking into the electric fan conversion (deleting the belt driven fan). Instead of wiring in new relays, couldn't you just install the lower temperature switch and use the AC condensor fan wiring to power the new fan? (i deleted my AC)



My assumption is that the AC condensor fan kicks in at a certain engine temperature to help with cooling regardless of whther the AC is ON. If this is true, the AC fan wiring could be fed to the replacement electric radiator fan.

[m3f_WRXEATR_c6f1d80be6]

Hi all,


I'm looking into the electric fan conversion (deleting the belt driven fan). Instead of wiring in new relays, couldn't you just install the lower temperature switch and use the AC condensor fan wiring to power the new fan? (i deleted my AC)


My assumption is that the AC condensor fan kicks in at a certain engine temperature to help with cooling regardless of whther the AC is ON. If this is true, the AC fan wiring could be fed to the replacement electric radiator fan.


What belt driven fan?


Your mechanical fan is viscous, and the aux fan is already electrical. (triggered by coolant temp and misc. AC inputs.)

[m3f_enderw88_23d4b6eb24]

What belt driven fan?


Your mechanical fan is viscous, and the aux fan is already electrical. (triggered by coolant temp and misc. AC inputs.)


Yeah I almost bit on this too, but the water pump pulley is belt driven which drives the fan, so...taken to an extreme I guess you could say you had a crankshaft driven fan...Oh and your sig picture haunts my dreams...


OP, your idea on using that wiring for the fan is fine. You may want to very that the circuitry still works. Make doubly sure you use good waterproof connectors to hook up the fan. the PO of may car did exactly what you are saying, but he used cheap hardware store housing connectors on the bottom of the radiator. First rainstorm they shorted. I corrected that with properly fitted wirepack connectors.

[m3f_cmcon98_d61dd8ea87]

Your idea will work fine, but first:



Are you autocrossing or tracking your car, or is your car heavily modded? If not, and it's running hot, something is wrong.



If your car is basically stock and street driven only, you really don't need to add more electric fans. Before you add more electric fans, consider that electric motors draw comparatively huge amps, and any tiny HP that you free up by removing the engine-driven fan are partially absorbed by the extra drag imposed by the alternator when the additional electric fans activate.



In my experience (over 300,000 miles spanning two cars) 6-cylinder E36s cool pretty well as long as the cooling system is clean and in good condition. This means a fresh radiator, thermostat, and water pump, and all temp switches, relays, electric fan, and fan clutch (on the viscous fan) working properly.

[m3f_enderw88_23d4b6eb24]

Before you add more electric fans, consider that electric motors draw comparatively huge amps, and any tiny HP that you free up by removing the engine-driven fan are partially absorbed by the extra drag imposed by the alternator when the additional electric fans activate.



Holy energy conservation Batman! How dare you imply that the Church of the Deleted Fan can actually consume power!



In all seriousness though, unless you are less than a tenth of a second off FTD in your class, this will not help you and will probably only hurt you when something fails and you don't know it until the temperature meter pegs.



For a purely street driven car it is just silly.

[m3f_Bimmerman3_4f9a469965]

The only real reason to go with an electric fan instead of the clutch fan is to eliminate potential failure points. The eFan is only really worth it if you get one of the super high flow ones, otherwise you're flowing less air than a stock clutched fan through the radiator.


I deleted mine because I had no idea how old it was and it was wobbling (turned out the WP shat the bed, but w/e). I don't think I gained any horsepower, and it wasn't my intention either.

[m3f_marvinstoc_6f75503062]

The installed 'AC' fan comes on with the AC compressor, and also with a high temperature condition (if the mechanical fan fails or towing a trailer up hill).



Bottom line is you can remove the mechanical fan and do nothing else. Just keep your eyes on the thermostat, as you no longer have redundancy.

[m3f_cmcon98_d61dd8ea87]

Keep in mind that the reason your E36 has an electric fan AND a clutch fan has nothing to do with redundancy. They do two different jobs.



The electric fan is primarily a condenser fan which moves air through the A/C condenser when the car is stopped or moving slowly with the A/C on. The A/C switch also activates the electric fan.



The engine driven clutch fan is for pulling air through the radiator; the viscous clutch engages the fan by figuratively 'coupling' it to the water pump shaft when the air coming through the radiator reaches a certain temperature.



If the A/C is off and the radiator coolant temp reaches a certain temp, the electric fan is activated. By the time this happens, the clutch fan will (should) already be engaged. The electric fan then supplements the clutch fan.



Without the electric fan, the A/C won't work well when stopped or driving at low speed (and the engine will run hot because, with A/C on, the condenser will transfer heat to the radiator, thus heating the coolant.



Without the engine fan, in hot weather, sitting in traffic with the A/C on, the heat from the condenser is being blown into the radiator by the electric fan. Eventually, the coolant temp will start to rise, and the electric fan won't be able to keep up. If you add more electric fans, the temp will stay under control, but you'll have the additional wiring and complication of the additional fan(s).



For street driving, I think the simplest and most reliable setup is the stock setup with everything working properly.

[m3f_enderw88_23d4b6eb24]

For street driving, I think the simplest and most reliable setup is the stock setup with everything working properly.



:thumbsup2:

[m3f_marvinstoc_6f75503062]

I'll say it again, as I'm currently running without mechanical fan. The electric fan comes on to keep engine at correct temperature, with or without AC being on.


The installed 'AC' fan comes on with the AC compressor, and also with a high temperature condition (if the mechanical fan fails or towing a trailer up hill).


Bottom line is you can remove the mechanical fan and do nothing else. Just keep your eyes on the thermostat, as you no longer have redundancy.

[m3f_hufflepuff_e935609de1]

Added details in the original post. Please let me know if this has been helpful or if it requires clarification. the advantages of the aftermarket fan are:



-reduced rotating mass on engine

-only operates when needed

-lighter than factory A/C fan

-can use on vehicles with A/C removed

-cheaper than replacement A/C fan

-if the oem fan clutch fails, the blades have the potential to damage the radiator and/or hood.

-no "truck" sounding cold starts

[m3f_hufflepuff_e935609de1]

Your idea will work fine, but first:



Are you autocrossing or tracking your car, or is your car heavily modded? If not, and it's running hot, something is wrong.



If your car is basically stock and street driven only, you really don't need to add more electric fans. Before you add more electric fans, consider that electric motors draw comparatively huge amps, and any tiny HP that you free up by removing the engine-driven fan are partially absorbed by the extra drag imposed by the alternator when the additional electric fans activate.



In my experience (over 300,000 miles spanning two cars) 6-cylinder E36s cool pretty well as long as the cooling system is clean and in good condition. This means a fresh radiator, thermostat, and water pump, and all temp switches, relays, electric fan, and fan clutch (on the viscous fan) working properly.





my car is used for autocrossing, track days, and DD.