Aux. Fan Resistor

#1

This weekend I plan on reinstalling my auxiliary fan in front of the radiator and eliminating the mechanical fan and the A/C condensor. I just read some old posts using the search function, but I still have a question:

It sounds like if my radiator temperature sensor is working properly, if I just hook everything back up with the OEM wiring harnesses, my aux. fan will run on low with the A/C button pushed in (and a slider slid to "on"). If the radiator gets really hot, it will send a signal to bypass the resistor mounted on the fan and consequently run the fan on high. Would y’all suggest going the plug-and-play route with dual fan speeds or changing the wiring so the fan always runs on high?

Thanks,
Sasha

P.S. I ordered the varioius OEM brackets for mounting the aux. fan without the A/C condensor in place. They will help me, but I’ll still need to install a piece of aluminum angle as an interface between the OEM mounts for the condensor (horizontal) and the tops of the brackets on the aux. fan (vertical).

#2

Great questions. I’m going to be doing this stuff soon as well.

Sasha, be sure to get some photos of this.

Good Luck and thanks.
Scott

#3

Ex36 wrote:

Actually, there’s holes in the front clip that aren’t used when you have a condensor (are are hard to see), but are used with the condensor delete bracket. If, in the middle of all the house chores, I get a chance, I’ll take a picture tomorrow.

#4

Ex36 wrote:

[quote]This weekend I plan on reinstalling my auxiliary fan in front of the radiator and eliminating the mechanical fan and the A/C condensor. I just read some old posts using the search function, but I still have a question:

It sounds like if my radiator temperature sensor is working properly, if I just hook everything back up with the OEM wiring harnesses, my aux. fan will run on low with the A/C button pushed in (and a slider slid to "on"). If the radiator gets really hot, it will send a signal to bypass the resistor mounted on the fan and consequently run the fan on high. Would y’all suggest going the plug-and-play route with dual fan speeds or changing the wiring so the fan always runs on high?

Thanks,
Sasha

P.S. I ordered the varioius OEM brackets for mounting the aux. fan without the A/C condensor in place. They will help me, but I’ll still need to install a piece of aluminum angle as an interface between the OEM mounts for the condensor (horizontal) and the tops of the brackets on the aux. fan (vertical).[/quote]
Run it without the resistor as the resistor is an item that tends to burn out. One less electrical gremlin to bite you in the A$$ when you don’t need it.

#5

Well, one less electrical gremlin unless I introduce another with my dumb-ass wiring ability!:sick: So should I just cut the wires on each side of the resistor and splice in a new wire in its place?

Sasha

#6

Sasha,

Check out the following link - http://shark.armchair.mb.ca/~dave/BMW/e30/

Page 124 (at least for an '87) shows the fan wiring circuit. It looks like you can jump the resistor so the fan will run on high speed when either the low speed or high speed circuits are activated.

Or you could possibly reduce other gremlins by wiring in a new fan relay (Advance/Auto Zone for about $30) which allows you to bypass all the stock stuff. You can wire directly to the AC switch (yellow lead - reach behind the console - push out the snowflake and you will see it). This is the hot lead.

I also wired in an adjustable temp sensor (included with the relay) so the fan will come on at the desired temp if you forget to push the switch. I’d be happy to share a diagram of what I did if you want it.

Ed

#7

You can disconnect the 3-pin connector going to the radiator temp sensor and then just run a switch (rated for 15A) that sends 12V to the high speed wire. Then you don’t have to worry about removing the resistor.

One of the wires carries 12V and the sensor in the radiator determines whether to send that 12V to the high speed or low speed wire.

I have a switch that just turns on the high speed for when I’m sitting idle on the grid. It works just fine.

#8

Ed, I’d like to check out the diagram.

Thanks
Scott

edavidson wrote:

[quote]Sasha,

Or you could possibly reduce other gremlins by wiring in a new fan relay (Advance/Auto Zone for about $30) which allows you to bypass all the stock stuff. You can wire directly to the AC switch (yellow lead - reach behind the console - push out the snowflake and you will see it). This is the hot lead.

I also wired in an adjustable temp sensor (included with the relay) so the fan will come on at the desired temp if you forget to push the switch. I’d be happy to share a diagram of what I did if you want it.

Ed[/quote]

#9

Thanks for the advice. I looked at the wiring diagram and it does indeed look like I can just replace the resistor with a wire; then no matter which switch (normal or hot coolant) is sending the power, it will run at high speed.

Sasha

#10

I finished the install today. For those who have it coming up, here are a few notes:

-I ordered all the parts from the RealOEM page copied elsewhere in the forum. If you’re judicious you could skip ordering the attachment hardware for the upper brackets (but you need each of the brackets). The total for all the parts was only around $19.00, so I’d just recommend ordering everything. You could scavenge some of these parts from the condensor, but the rubber isolation pieces are likely hard and not worth extracting from the condensor. Once you remove the condensor, you could also move one of the rubber bumpers attached to the body at the radiator opening, but I think this might be difficult to do without cracking the plastic anchors that hold the rubber discs to the frame. I did need to go to Lowe’s and purchase a 6mm bolt and self-locking nut to attach the metal disk that just sits on top of these rubber bumpers to the bottom of the fan.

-As Dan mentioned, you can re-use both the upper bolts that hold the condensor as well as the threaded metal tabs that receive these bolts. They all just need to be moved to the underside of the top body strut across the radiator opening (all the holes are already in the body where they need to be). Then the fan fits fine with no additional fabrication required, unlike I first reported.

-I removed the resistor on the fan and soldered the two leads from either side of the resistor together. Once this is done, however, you’ll draw more current because the fan always runs on high. I blew the 15A #3 fuse immediately and then replaced it with a 30A (the Bentley seemed to indicate this shouldn’t be a problem–if anyone disagrees let me know). Now my A/C button and slider turns the fan on and off and it blows like hell.

-I was able to do the install without removing the radiator. I simply took the upper bolts out and pulled it back to slip the aux. fan in front. I did remove all the front plastic trim pieces, however, to give the clearance I needed to tighten the fasteners for the fan from above the front bumper.

-The total time for this project was probably on the order of 2.5 to 3 hours. As usual, I could now do another in about 25 minutes.

Good luck,
Sasha