Want to start of by saying that I've searched all over the we and forums but could not find anything similar to my issue and hope some one can help. Any help is appreciated.

i just installed a new alternator, battery and spark plugs from Autozone on my 07 525i with 98k miles. the car runs great and smooth but for some reason when i turn on the ac, front and rear defrost and head lights my RPM's start to move and bounce up and down and vibrate? if everything is off then everything is normal. its very annoying and cant figure it out. hope someone has an idea or could lead me the right way. Thanks

 

When all those accessories are turned on, essentially, you are putting lot of load on the alternator. I suspect the alternator is the culprit. While all those accessories are turned on, test the alternator output. You can test the voltage at jump terminal in engine compartment area. Voltage should read steadily just above 14.0V.

 

Ill have to check that out PCY. i was reading on another forum cite and some mentioned the spark plugs? would that be possible?

 

You need to go thru all possible culprits and rule-out each of those one by one by the process of elimination.

If the alternator output is steadily around 14V and the symptoms persist with all those accessories are on, then you can rule-out the alternator.

If the spark plugs were never changed on that car, it's due for new spark plugs anyway; go ahead and change the spark plugs.

 

just got back from the BMW dealership were my mechanic works and i asked him to bump up my rpms just a tad and now my car feels great! no more vibration at ALL even when the AC, Lights and defrost are on. Thanks for advice PCY