alternator or dead battery?

Brett Krehling · 04-13-2019, 06:44 PM

was driving my 2011 135i when a red battery light popped up .shortly after a Christmas tree of lights popped up with all sorts of errors. the car then popped out of gear and would not start again. so if i replace my alternator how do i recharge the battery or can i jump start it?

mackeroni · 04-13-2019, 09:24 PM

Quote:

Originally Posted by Brett Krehling

was driving my 2011 135i when a red battery light popped up .shortly after a Christmas tree of lights popped up with all sorts of errors. the car then popped out of gear and would not start again. so if i replace my alternator how do i recharge the battery or can i jump start it?

How do you know the alternator needs to be replaced? Based on your description of the problem, I recommend you find a good local independent shop to figure out what repairs are needed. Good luck.

Peace... Mack

NVHoo · 04-14-2019, 08:22 AM

Usually if the battery goes dead while running, it is the alternator. However, the battery could have an internal short circuit. Disconnect the battery, jump start the car, remove jumper cables, if the car dies it is the alternator.

NorthernDancer · 04-14-2019, 11:26 AM

Quote:

Originally Posted by NVHoo

Usually if the battery goes dead while running, it is the alternator. However, the battery could have an internal short circuit. Disconnect the battery, jump start the car, remove jumper cables, if the car dies it is the alternator.

No no no no no. We don't do that anymore. Like said here, take you car to a good BMW indy or even the dealer. Quite often this problem is caused by a bad ground wire between chassis and engine I believe.
And, buy yourself a good battery maintainer (Deltran, CTEK, Schumacher)

JimD · 04-15-2019, 01:27 PM

My alternator died on my 2009 128i. I got the battery symbol at startup but thought I could go to work and then to Walmart for a battery. But it kept doing more goofy stuff. Windshield wipers started going for no reason. Lots of lights on the dash flashed. After maybe 10 miles, I decided I had to get a battery now and tried to make it to a Walmart - or anywhere. It died on the side of the road. I called AAA, they sent the battery guy. But he told me it seemed like it was the alternator. The battery was a little low, like 12V or 12.2. So I had it towed to an independent who replaced the alternator, for $800.

BMWs are HUGELY babies about electrical. I've had a battery die before but it happened after maybe 100 miles and only after the battery was at a really low voltage, like 11V. BMWs scream at you and then die quickly.

I haven't looked closely at the alternator and how it is installed but the independent did it in a day. I think they bought an expensive alternator. I saw them for less than $300. But maybe they weren't as good. I think it was about $600 for the alternator and $200 labor. I could have done it but I didn't have another vehicle to use to go get parts.

dtla1 · 04-15-2019, 04:25 PM

Someone else kind of mentioned it, but check:

1. The Ground strap from the engine to the subframe. It's a braided cable one the driver's side of the engine, near the subframe, kinda underneath the throttle body. It tends to corrode and degrade with time and engine movement and will eventually fail, sometimes catastrophically similar to what your described.

2. Also check the main power cable that runs under the air filter box and to the jump start post on the passenger side. This one is also known to fray and eventually fail, also catastrophically similar.

Final general electrical comments, check to see if any open recalls (for the battery to fuse box cable recall from way back) as well as if your main relay at the fuse box may have gone bad.

And good luck.

04-13-2019, 06:44 PM	#1
Brett Krehling New Member 16 Rep 20 Posts Drives: 2011 Bmw 135i Join Date: Jun 2018 Location: Pennsylvania iTrader: (0)	was driving my 2011 135i when a red battery light popped up .shortly after a Christmas tree of lights popped up with all sorts of errors. the car then popped out of gear and would not start again. so if i replace my alternator how do i recharge the battery or can i jump start it?
	Appreciate 0 Tweet Quote

04-14-2019, 08:22 AM	#3
NVHoo Second Lieutenant 159 Rep 282 Posts Drives: 2011 128i red convertible Join Date: Feb 2015 Location: Las Vegas iTrader: (0)	Usually if the battery goes dead while running, it is the alternator. However, the battery could have an internal short circuit. Disconnect the battery, jump start the car, remove jumper cables, if the car dies it is the alternator.
	Appreciate 0 Quote

04-15-2019, 01:27 PM	#5
JimD Brigadier General 368 Rep 3,547 Posts Drives: 128i convertible Join Date: Apr 2009 Location: Lexington, SC iTrader: (0)	My alternator died on my 2009 128i. I got the battery symbol at startup but thought I could go to work and then to Walmart for a battery. But it kept doing more goofy stuff. Windshield wipers started going for no reason. Lots of lights on the dash flashed. After maybe 10 miles, I decided I had to get a battery now and tried to make it to a Walmart - or anywhere. It died on the side of the road. I called AAA, they sent the battery guy. But he told me it seemed like it was the alternator. The battery was a little low, like 12V or 12.2. So I had it towed to an independent who replaced the alternator, for $800. BMWs are HUGELY babies about electrical. I've had a battery die before but it happened after maybe 100 miles and only after the battery was at a really low voltage, like 11V. BMWs scream at you and then die quickly. I haven't looked closely at the alternator and how it is installed but the independent did it in a day. I think they bought an expensive alternator. I saw them for less than $300. But maybe they weren't as good. I think it was about $600 for the alternator and $200 labor. I could have done it but I didn't have another vehicle to use to go get parts. __________________ 128i Convertible, MT, Alpine White, Black Top, Taupe Leatherette, Walnut, Sport Ordered 5/22/09, Completed 6/4/09, At Port 6/9/09, On the Georgia Highway 6/13/09, Ship Arrived Charleston 6/24/09 at 10pm, PCD 7/21/09
	Appreciate 0 Quote

04-15-2019, 04:25 PM	#6
dtla1 Colonel 828 Rep 2,232 Posts Drives: 2011 135i, Space Grey Join Date: Apr 2014 Location: Silicon Valley iTrader: (2)	Someone else kind of mentioned it, but check: 1. The Ground strap from the engine to the subframe. It's a braided cable one the driver's side of the engine, near the subframe, kinda underneath the throttle body. It tends to corrode and degrade with time and engine movement and will eventually fail, sometimes catastrophically similar to what your described. 2. Also check the main power cable that runs under the air filter box and to the jump start post on the passenger side. This one is also known to fray and eventually fail, also catastrophically similar. Final general electrical comments, check to see if any open recalls (for the battery to fuse box cable recall from way back) as well as if your main relay at the fuse box may have gone bad. And good luck.
	Appreciate 0 Quote