Hey guys,

I bought my 2005 MCS 2 years ago with 38k miles. Last November, I went out to run some errands and ended up getting stranded at the store. I had a friend come to jump start the car, but our jumper cables ended up being crap so we had to push start the car. I drove to the nearest European auto shop and they ran diagnostics on the battery and alternator. They told me that I needed a new battery and a new alternator. The guys there seemed shady and they quoted me $1500 for the new alternator. I passed on that and had them install a new battery.

I drove the car without issues until June this year. The first problem I had was that the buttons on my key stopped working, which was fine because I can still open/lock the car the old fashioned way by putting the key in the lock.

The next issue I had that started in June (after my key went out) was that the battery seemed to be slowly draining over about a week. This was annoying, but being strapped for cash, I didn't take it to a shop and simply put the battery on the trickle charger once a week.

Last month, July, I was fed up with having to frequently charge the battery so I emailed Danny at Minicorsa. I figured that my Alternator was bad since that's what the shady European Auto guys had told me, and Danny quoted me 700 to replace it (much lower than the other quote of 1500 from the other guys). So I took the car to Danny and he told me that the alternator was actually fine and I should take the battery back to the other shop because it should be under warranty still.

I was reluctant to do this since the other shop had told me before that I needed a new alternator and I'm sure they would have told me that was the reason for the battery failing again. I had a new battery in my other car that I rarely drive, so I threw that in the cooper and noticed the same slow drain.

At this point I'm thinking of taking the car to another shop to have everything tested and checked. I've had one shady shop tell me I need a new alternator and one reputable place (minicorsa) tell me that the alternator is fine.

Could it be another electrical issue somewhere draining the battery? is the key going out possibly related?

Also if it matters or might be related, the car's idle went up from 800 to around 1000 last month, which I thought was weird but didn't bother me too much.

Sorry about the novel and thanks in advance for any help!

 

Do you have an aftermarket stereo, or amp?

I know, seems totally unrelated to the issue, but there are rumours going around on this thread that aftermarket stereos can create a problem depending on their wiring.... I have had the issue with the remote not unlocking/locking the car. But it's not frequent. I've also had other random problems come and go, and someone said check my stereo.

You could also have a bad ground somewhere, moisture, god knows. Germans made this car way too complex and complicated.

 

yes the car has an aftermarket pioneer stereo and a subwoofer with an amplifier. I disconnected the sub and amp a few weeks ago thinking it could have been the issue, but the battery drain continued. Maybe it could be the stereo?

I'll start checking grounds

 

When I created a post mentioning my weird electrical problems a few people chimmed in and pointed at my sony stereo, and said disconnect it and see if the problem goes away.

I'm still baffled about how everything was fine for the past 8 months, and now things are acting up. And it's so random like once a week, I wouldn't even know if that fixed the issue or it just went away on its own.

The stock stereo/speakers are ****, I've gotten birthday cards that had better sound than my mini came with.

 

Yes it can be the stereo. My other car, a '36 Chevy Coupe, had a similar slow drain issue after I completed a frame off restoration. This was very disturbing since I installed a new wiring harness in the car during the restoration. It turned out that the "new" stereo I installed was defective. A stereo will typically draw around 10mA or so as part of the memory presets which won't affect starting for months. I found mine was drawing about a 1/2 amp. Disconnected the stereo and my problem went away, so I put another new stereo in and no longer have any issues.
A quick way to fine the problem is to check your draw on the battery with an ohm meter and start pulling fuses. When the draw goes away, you will have found your bad circuit and you can troubleshoot individual components at that time.

 

Thanks for the replies guys, I'll disconnect the stereo and see what happens. If that doesn't work I'll pull out the old multimeter and start troubleshooting

 

I'm pretty sure that 1936 chevy had a better sound system than any factory mini lol.

And a bad ground can be the cause of your remote not working, but doubt it would cause the battery to drain.

btw, how did you connect your amp? How did you get the power supply wire from the battery into the cabin?

 

I was able to fit the amp in the small compartment on the driver side in the trunk area, so I just had to run the power supply wire under the panel into the compartment to the amp.

 

Alright I have some updates.

I unplugged the aftermarket stereo and still experienced a battery drain over the course of a day of regular driving.

I plugged it back in and pulled out my multimeter. The draw from the battery with everything off was 0.7 milliamps. too high? normal?

With the battery fully charged, it reads 12.6 volts with the car off. With the car running and under a load (high beams, air conditioner on) revving at 2k rpms, the voltage goes down to around 12 volts.

Doesn't this point to a faulty alternator?

 

You should be reading 13.5 - 14 volts at the battery with the car running and under load. Sounds like the alternator to me. I assume no check engine light?

 

Can you provide a bit more information regarding your driving habits? Mostly short, around town drives? Is work close by? My Uncle had a problem with a low battery as he only used the car a couple times a week and did not drive far. The car would work well for months then gradually the battery would wear down. You can also go to your FLAPS (Favorite Local Auto Parts Store) and most of them will check your battery and charging system for free. It would be a cheap way to isolate the problem as being an alternator, battery, or both.

 

Check engine light isn't on.

I drive the car every day for short trips around town, rarely driving for more than 20 minutes at a time; most of my trips are around 10 minutes.

I'm going to head down to the Auto parts store to get everything tested.