I've read through a bunch of the electrical threads and haven't seen this one yet. I'll try to provide as much detail as I can to help.

I have an 02' Cooper and when I went to start my car last night, everything went dead. Everything (indicator lights, radio on, etc) looked normal when I turned the key to ON, but when I went to START everything died. After that, I hear key in ignition tones and only the air bag light comes on when the key is in ACC but after that... nothing. Power locks do not work, headlights do not come on, but the dash lights do when I try to turn on the headlights. No interior lights (reading or dome) work. Basically ALMOST nothing electrical works except the key in ignition chimes, dash back lights when the headlights are in the on position, and the airbag light in the ACC position. I can hear relays clicking when I've tried certain things but nothing comes on. I've checked all the fuses under the hood and many in the kick panel. All have been good. I checked the battery voltage and it was 12.5V, but its also about a month old anyway. Just out of sheer trial and error this morning I tried to jump it. Here's where it gets a little weird... The first time I turn to ON, all the lights and radio etc. come on. So I'm thinking GREAT!... But then I go to START and everything dies again. After that, even with the jumper cables still connected... no power again... no lights, just as described above.

I'm currently trying to get BMW TIS working (so far its in SWEDISH, despite selecting ENGLISH (USA)) to try and troubleshoot but after the weird behavior this morning I'm suspecting a faulty ignition switch. I have a basic electronics understanding but am not expert by any means and I have no idea if this car has had any electrical problem history. I've only owned it for about 16 months.

Has anyone seen this before? Any ideas? Any help is vastly appreciated!

 

Slightly more info to add... ALL fuses interior and under the hood tested good (rather than just visual inspection). I get 12.6V across the battery, across the fuse box and from positive terminal to the frame.

Also, it seems the very first tone in the key in ignition tone is a different note than all of the ones that come after... maybe an error tone?

 

Please advise what is the voltage across the (B+) battery terminal and (B+) battery clamp.

Note the voltage when the key is in the start position only!

Repeat the same on the (B-) battery terminal and (B-) battery clamp.

 

To clarify, when testing voltage in the start position, you want the key turned AND HELD in the start position while testing voltage correct?

I'm not sure where you are asking me to measure... do you want one lead on the + battery terminal and one to the + battery clamp? I outside of the clamp is a little oxidized and doubtful that a good connection can be made and it doesn't seem that you would get a voltage reading with both on the plus side.

 

Confirmed!

one lead on the + battery terminal and one to the + battery clamp

Do the same on the - battery terminal and clamp as well

Both terminals must be done with the key in the start position

Report the value on the meter in DC volts under the above conditions.

 

Remove your battery leads, and take a wire brush to your battery terminal and to your battery wire clamps to rmove the corrosion. It sounds like enough juice is getting to the instruments, but when you try starting, the additional current is cutting the connection. Also get the voltage across the battery when disconnected. If less than 13.2v, charge it back up again before reconnecting.

 

Ok, Thanks for the suggestions... Frenchie's post got me messing around and the clamps are pretty corroded. My dad and I ended up removing my battery and connecting my clamps to his battery via jumper cables. This gave me power, but not enough to start. Then we cleaned the terminals and clamps with a brush and reconnected everything and it started right up! I'm glad I don't have to lose faith in German engineering. :-) I'm really concern that things would be that corroded however, my battery is about a month old and some really corroded cables were said to have been replaced at the same time. I've gotta check the parts summary/bill before I go accusing. Any suggestions on preventing corrosion? I live in a dry climate if that make any difference.

 

Go to an auto store and get those red and green anti-corrosion rings to place over the terminals. The are felt coated with some sort og chemical. They work real well in preventing this problem.

 

I am happy the situation is resolved; we missed out on the opportunity to demonstrate the effectiveness of the voltage drop test!

When the terminal and clamp are the same electrically, there will not be any voltage on the meter between the battery post and the clamp! (.01 VDC max)

The greater the resistance between these two points the greater the voltage will be on the meter!

This is absolutely the best method the determine if the electrical connection is good; personally I never believe my eyes choosing instead to believe my meter.

The voltage of a fully charged battery is 12.6 VDC.!

 

Batteries will be at 13.2 volts immediately after charging and will then slowly drop to 12.6v.

 

The surface charge does not count

12.6 - 100% charged

12.4 - 75% charged

12.2 - 50% charged

12.0 - 25% charged

Believe it or not!