Aux Fan on AC Condenser Upgrade

[Chilezen]

I can't remember where I've seen this, so I have to ask: what later BMW has the preferred AUX fan to replace the bulky E30 one?

Or is it better to use a modern, brand-new, slim fan up front?
I'd like to know more about wiring in an aftermarket fan and retain the low and high speed functions. I've seen most installs just delete the low/high capability, because they either don't know or don't care to do it OEM style. I would like to know.

And I'm not doing this to replace the engine fan. I want this to remain as intended, for the AC, and as a supplemental fan when the engine's hot.
Thanks.

[tomstin]

I used this thread as a guide when I updated my AC and used an aftermarket fan and wired it to come on high. I don't see why you couldn't wire an aftermarket fan the same was as the original.

https://www.r3vlimited.com/board/forum/e30-technical-forums/e30-faq-and-diy/213651-the-detailed-e30-r-134a-conversion-thread-diy?t=246743

[moatilliatta]

You just need a aux fan resistor and wire it up like factory.

I have a 2000+ cfm spal main electric fan wired up this way but couldn’t keep resisters from failing… Tried a few from different models and some from Mercedes.

Any spec on what stock Aux fan CFM is?

[varg]

Doubtful. It's fairly difficult to measure such a thing, you need a calibrated flow meter large enough to measure the flow across a range of pressures to establish a curve so unless an OEM rating exists you probably won't find any ratings. FWIW fan ratings are usually basically made up if they don't specify the pressure at which the measurement was made, just holding an anemometer behind a fan and calling it a day is worthless since it only measures local flow and the distribution across the swept area is not uniform. Spal's ratings seem pretty trustworthy.