My wife noticed last month that when turning the ac/heat on high it would only blow medium speed (occasionally high when it wants to). I thought this was an easy fix so I ordered the blower motor and module that sits on it. Dreading putting it on I finally was bored enough and put them on last weekend. Tested it out and it seemed as if it fixed the issue. Today I decided to pull it out of the garage for the first time since Saturday and drive it to work and guess what the same initial issue. It blows high when on defrost but not on any other setting. When driving home I hit a bump and it just starting blowing high out of no where. It is not the iDrive settings.

Now I am puzzled I think only because I am getting lazy (have too many cars in the driveway and it seems I am always turning a wrench). I have not hooked INPA up to it yet but I am pretty sure it will not tell me anything. Has anyone else had this issue before? Could it be the thermo in the dash? I would say no since it just popped in after high a bump. Is there a mechanism the tells the blower motor to blow at a higher speed other than the module (I know its not called a module but my mind is drawing a blank at the moment) sitting on it. Could it be that I need to reset something after changing the resistor? I am going to charge my battery just in case tonight because we hardly drive it. Maybe that can be the issue. It cant be the micro-filter because it stays in the garage and plus it was change about 3 months ago.

Any thoughts let me know. I am in no hurry since it never leaves the garage. 05 530i 150K

 

I think I found the solution. Last night I charged my battery to 100%. I drove it all day today and not one issue with the the fan motor blowing at half speed. I think remember reading some where that if your batteries charge is below a certain threshold your heat (using the defrost) will be the only thing that blows at high speed due to cold winters (safety). Every other setting will only blow at a certain speed until the battery is over the threshold.

I will drive it for another couple days and report back my findings.