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Hi all, does anyone know if the a/c pusher fan is temp controlled the reason I'm asking is I tested it a month or so ago by pressing the a/c button and it worked fine before it became winter here in the UK
I went to check it today usual method press a/c button and nothing happened after 5 mins or so.
I've read In a few places that the ambient temp has to be above 10 degrees for the a/c to trigger electric fan.

2003 530i

Much appreciated regards Callum.

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There is a startup test on your MY: The ECU briefly spins the aux fan on startup. Not sure if it's only on a cold start.

There may be a low-temp lockout. Perhaps someone smarter than I will comment.

The ECU controls fan speed based on the radiator outlet temp.
 

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A 530 will have the PWM fan, controlled by the DME. The DME uses two inputs to decide how fast to command the auxiliary fan to run: radiator outlet temperature and A/C system pressure. So far as A/C is concerned, the DME starts the fan at lowest speed at 5 bar, and ramps up over a dozen or so steps as pressure increases.

There is a low ambient temperature cut-off below which the HVAC panel (IHKA in BMW-speak) will not energize A/C. I'm pretty sure that you're correct that 10C is that limit. So below that, no A/C activation & therefore the aux fan won't be run. A fine point though, it's the DME that decides to run the aux fan based on an A/C pressure signal sent from the IHKA; not the IHKA itself, directly. For instance, there was a thread a few months ago where the aux fan seemed to be inop and the root cause was low R134a charge. There was enough pressure for the IHKA to OK energizing the A/C clutch, but not enough refrigerant to pump up to 5 bar, so the DME wouldn't run the fan.

With the earlier design 3 stage fan with relays and resistors the IHKA does activate the aux fan itself directly, stage 1, when the A/C clutch is energized - pressure is not "in the loop." A pressure switch energizes stage 2 if/when pressure reaches 20 bar. The DME is not in the control loop.
 

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Wingnut
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one thing regarding the OP and edjack's posts..is there a low temp lockout for the test of the PWM fan? upon startup, the DME is sposed to command the fan up to speed then shut it off, monitoring the back EMF to test if it came up to speed, regardless of whether the AC is turned on or not.
 
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