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Check Engine Light on After Alternator Replacement

(1990 BMW 325i)
in Vancouver, WA on December 25, 2010
Hello, I have to tell you the whole story here so you will understand my Frustration!!!
Had Professional Shop on Monday December 20th 2010 inspect my vehicle for a possible sale to another person. Not much came out of the inspection, other than under carriage was too dirty for the buyer...Strange!!

Now here is the kicker!! This may be a coincidence but.....On Tuesday Dec. 21st went to the store and Radio started to go off and on....thought that was weird; then the check engine light started to blink on and off. Parked in the store lot and turned off the engine. Tried to start the engine again and Battery was completely dead. Got a jump from a nice man and drove the car home where I checked to see if the Alternator was putting out current to the was not, and Battery was down to 8 Volts. I charged the existing Battery back up to its capacity. I took the old Alternatoir out and ordered a new Alternator and put it in Wednesday 22nd. After I put in the new Alternator the Check Engine light is on with the car running....the new Alternator is charging the Battery fine. Before I took the car into the place that inspected it, it was running great and Alternator was charging.

Could the shop have done something to blow out the Alternator and harm the Charging system while they were doing the Inspection? Maybe Coil? But if that were the case the car would not even start. I'm really baffled on this one. I would appreciate any input.
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Popular Answer
on December 25, 2010
I would like to say it was purely coincidence, alternators are too common on these engines. Coil has absolutely no direct connection to the alternator. If the battery is healthy, it would take time before the symptoms are noticeable. As for the engine warning light, possibly a battery power reset, removing the battery terminal for 10 minutes and recheck afterwards and also check all plug connections especially to the AFM, tank vent valve and oil filter housing
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on December 25, 2010
Thank you for your input. Could you tell me what the AFM is? You seem to know a lot about these BMW's. I will try the Battery Disconnect. When the nice man gave me the battery jump he connected the Negative Jumper on the Battery Negative pole instead of on a Ground point within the engine compartment. Would this have blown something in the Charging System?
on December 26, 2010
Hello Chow....I did what you suggested and disconnected the Battery Terminals for 10 minutes and........Qualla!!! The Check Engine Light WENT OUT!! Thank you. Now I know.....Good to know that the vehicle's Computer is working OK....I would think. Thank you again.
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