Must the aux/electric fan always run when AC is on?

2000 528iA

1.) Installed Dynavin D99
2.) AC Stopped engaging (compressor does not turn on)
3.) Removed D99 and updated firmware on ibus module of Dynavin
4.) AC still not engaging - HVAC module needs to be re-coded per Jeff (Dynavin)
5.) Connected to GT1 and somehow got it to write re-code the HVAC Module
6.) AC works fine now

Butttt the aux fan does not turn on. I ran a test from the DME module and it spun up fine, so I know it works fine, but it wont turn on when the AC is on. At what point should that fan turn on? Should I be worried that's it's not turning on when the compressor kicks on?

FWIW I had the AC on for 20 min idling - never spun up once - I was monitoring Oil/Coolant/Engine temps and they were right where they needed to be - So maybe that's why fan did not turn on?

The aux fan on the early cars ran all the while the A/C was on. Later cars were smarter.

Mine does not. 98 528

Originally Posted by kgorczyn

2000 528iA

1.) Installed Dynavin D99
2.) AC Stopped engaging (compressor does not turn on)
3.) Removed D99 and updated firmware on ibus module of Dynavin
4.) AC still not engaging - HVAC module needs to be re-coded per Jeff (Dynavin)
5.) Connected to GT1 and somehow got it to write re-code the HVAC Module
6.) AC works fine now

Butttt the aux fan does not turn on. I ran a test from the DME module and it spun up fine, so I know it works fine, but it wont turn on when the AC is on. At what point should that fan turn on? Should I be worried that's it's not turning on when the compressor kicks on?

FWIW I had the AC on for 20 min idling - never spun up once - I was monitoring Oil/Coolant/Engine temps and they were right where they needed to be - So maybe that's why fan did not turn on?

As soon as the A/C is turned on ans stays on while a/c is running, Same year /model as your car, Mine is MTranny ,but doubt that means anything different

Mine only comes on when the control module determines that it is needed not when the AC is turned on necessarily. Check the sensor in the bottom radiator hose. If mine is unplugged the fan runs all of the time regardless of the AC being on or not.

Originally Posted by Jim Rolando

Mine only comes on when the control module determines that it is needed not when the AC is turned on necessarily. Check the sensor in the bottom radiator hose. If mine is unplugged the fan runs all of the time regardless of the AC being on or not.

Awesome tip - I'll give it a shot - Thank you!

The M52 & M62 aux fans' operated differently than the M52TU/M62TU/M54 aux fans. See the info below for the latter:

What a lesson. Thank you gentlemen! Puts me at ease! Very valuable Info!

Mine only comes on when I have the "MAX AC" button on. It works great. But normally I have the a/c in Auto, 72 or 73. So it doesn't work very hard unless it's summer.