Last night whilst driving home a strange (grinding) noise appeared from the engine compartment... A moment later no power steering and battery light on the dash. When opened the bonnet I noticed the alternator freewheel lying on the floor (belt completely fine). I thought that somehow the alternator bearings must have seized and forced the freewheel off but NO the alternator shaft appears to rotate completely free! Why on earth did the above happened?
The new alternator should arrive tomorrow Is it a lot of hassle to change it? Any special tools needed if anyone has done the exercise before?
I just put the new (second hand)alternator(150A) in. All good - 14.0V to the battery terminals HOWEVER the battery light is still on!
Does anyone know how to reset it? (Obviously this is not run by the alternator voltage and I would assumed it has registered an error which my OBDII reader does not detect.
For those who are interested: I called Bosh (they supply the alternators to BMW) and apparently these alternators are fitted with one way clutch freewheels and what must have happened to mine is the actual freewheel bearings seized and literally disintegrated the pulley...
Try disconnecting both terminals from the battery, then with something metal join the 2 terminals together then turn the key to position 2 in the ignition. This will create a closed loop and totally discharge the system of power. Reconnect battery and see how it is.
I took the car to a BMW dealer yesterday. After about an hour of testing (!) I was told that both my battery and alternator are OK however there is a communication fault between the alternator and the ECU. They couldn't tell me what is causing this fault- need the car for one whole day to investigate!!!
Considering that it only takes 18 minutes to take the alternator out I'll maybe try swapping the voltage regulators with the old unit which I believe that is still OK electrical wise
Sounds like your just went into the BMW stealership and dropped your trousers and bent over. Did you try the full reset I told you about in previous post? I replaced an alternator on my e30 325i and had this same issue, constant battery light.
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