E87 Weak AC Blower

[Danch 35]

Hi all,

I'm having an issue with weak AC blower. If I increase the fan speed, it's still very weak. Almost feels like the fan speed control is not doing anything. I tried replacing the blower resistor with a second hand unit but no luck. 

I've lubricated the blower and it doesn't feel that stiff but still the same. The previous owner did say that the blower stopped working but he cleaned and fixed it. I didn't check if the blower is working in full speed when I bought the car :/

The only other thing that I can think of is that the battery was changed from 70AH to something else 3 years ago but never registered. I think it's 63AH model. I checked Bimmercode but the only options closer to 63AH are 70AH or 60AH AGM. It's currently showing 70AH 49% charge on Bimmerlink.

My next step would be to get a second hand blower and see if it does the trick.

Did anyone have similar issues before?

Thanks in advance for any help!

Danny

 

[C-130 Hercules 571]

Use a resistor that you know is good and swap it in. Still sounds like a bad resistor to me. 

[Danch 35]

@C-130 Hercules that's what I was thinking too. I just wasn't keen to buy a brand new resistor without knowing that that will fix the issue..

[The Bimmer 11]

I have a spare blower motor with new resistor from e90.

[Danch 35]

Pm'd 

[F10er 65]

If your car has an IBS sensor on the battery it might just be a weak battery.

If the IBS senses the battery is weak, it will tell the power management in the car to restrict or sometimes completely deactivate power consumers like the blower motor, heated seats and heated rear window. 

[F10er 65]

Screenshot from ISTA. If your battery is too small like you say it is, i would suspect this may be your problem. 

 

Edited August 23, 2023 by F10er

[Danch 35]

Thanks @F10er

I have driven the car for at least 2 hours today and it does seem odd that the battery state of charge is not really going above 50%. I'll try to get the battery health checked. 

Interestingly the seat heating still works so I'm not sure if this problem is because of ISTA. I will charge the battery overnight and try to register the battery to see if it makes any difference.

[F10er 65]

The power management will selectively restrict power to any of these functions so although your seat heating works, it may still be restricting the blower speed.

Start with the basics first like the battery. These cars MUST have a good battery of adequate size or there will be problems. 

Even a 70AH is too small really. I remember when i was working at a dealer when these cars were new, BMW were upgrading the 70ah batteries to a 90ah because the 70ah batteries were too small and causing a lot of issues.

I would be getting rid of that undersize battery personally and installing a new one. It may not be the issue now, but it will give you problems eventually. Preventative maintenance. 

Also have you scanned the car for fault codes?

[M3AN 4016]

Can you isolate/eliminate the battery by jumping another one to it, or plugging it into to a high amp charger?

If you did that, and the blower responded with more volume, then you'd know it was the battery. Right? Blower doesn't respond, your battery is fine, something else is borked?

Edited August 24, 2023 by M3AN

[Danch 35]

Thanks for all the replies! 

Thanks to @The Bimmer, I tried his blower motor resistor and the blower worked fine. The second hand unit I got must've been faulty as well.

Edited August 24, 2023 by Danch