Heater fan - acceleration

[thenorwegian]

Hi!

My 2003 2.5i have a strange problem.

The heating fan is working good, but when accelerating hard it slows down/stops and then comes back again.

Is this normal?

Is the heater controlled by vacuum?

Could this be caused by a vacuum leak?

 

[ph001]

It’s not controlled by vacuum as it just a 12v blower. I think you need to check alternator voltage when accelerating, maybe you have a bad voltage regulator or duff battery that’s screwing up the canbus.

 

[thenorwegian]

Maybe the voltage regulator is on the way out then.
Battery is almost new..

Thanks!

 

[colb]

Maybe its the blower resistor on its way out as that controls the fan speeds for the blower motor.
https://www.realoem.com/bmw/enUS/showparts?id=BT32-EUR-07-2003-E85-BMW-Z4_25i&diagId=64_1291
Not sure how you could test it before putting a new one in. Might be worth asking one of the guys who break Z's if they have a used part.

 

[thenorwegian]

Ok so I got in to the obd menu in the dash and selected the voltage monitor.

It sits around 14 so thats good.
When i accelerate hard the blower doesnt always slow down but when it does the voltage drops down to around 12.

Is 12 to low when accelerating? It stays at 14 most of the time.. But when it drops to 12 the blower stops.

So there seems to be a connection between blower stopping and voltage.

 

[Scooba_Steve]

So there seems to be a connection between blower stopping and voltage.

More likely just a symptom of the falling voltage, rather than the blower causing it.

 

[colb]

Might be the voltage regulator in the alternator going bad with that voltage drop when running causing the blower to slow down. See this thread for similar fault https://z4-forum.com/forum/viewtopic.php?f=3&t=124325&start=15
He got away with just changing the regulator pack on the alternator, cheaper than a recon unit. Just check the bearings on yours, if at all suspect or mega mileage then recon alternator may be the better option.

 

[ph001]

That’s kind of exactly what the efficient dynamics does on the E89! But you defo don’t have that on your car. Does sound like a duff alternator / regulator to me.

 

[thenorwegian]

Allright gonna try changing regulator.
The car have just driven 100k km so its a bit early for the alternator to be failing.