I have a 2008 Mini Cooper S. After being snowed in for 3 days, my MCS wouldn't start so we tried to jump my mini. I had to do this twice already when it was like 15 degrees, both times it started, I drove it to work and everything was fine. Now it won't start off a jump. We put it up to a battery charger and let it sit for awhile. And then it started... Finally. But it won't idle at all, not even feathering the gas. It just dies immediately. Help!!!

 

Did you test the battery after it started? A faulty or failing alternator can cause many problems, from a simple discharging of the battery to an engine drivability problem. There are a few signs and tests you can perform to determine if the alternator is the root cause of your problem. Always check the voltage of your charging system under load. Voltage should be within 13.2: 14.5 volts d/c. To load, have the engine running at idle, turn on the headlights and HVAC blower motor. Never disconnect a battery cable while the engine is running to test the alternator. You may cause damage to the alternator or other electrical components from the surge in amperage. Before performing any tests of your alternator, charge and test your battery. If the battery is faulty, your alternator tests will not be accurate.

So, first test the battery to make sure it's in good working condition. If it tests out fine, then move to the alternator. Was there a CEL (check engine light) on or any codes present in the system as well?

 

Sounds like a weak battery that on its way out, if you load test the battery at an autozone or parts store that will confirm you need a new one. Quick , easy test.

 

Thank you for this post. informative, succint, and friendly. A nice and welcome change from other forums, today.