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09-22-2016, 11:45 AM | #1 |
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Electrical problem on my Z4M Coupe ?
Hi guys,
I'm new here and I drive a Z4M Coupe that has a bit more that 70k miles on it. A couple weeks ago something weird happened. While I was driving on the freeway, the ABS, Brake and ASC lights came on for like 30 seconds then went away. I read the forums and assume this is a speed sensor on the rear wheels that is dirty, but I don't get to fixing it right away. About a week later, same scenario only at the end the brake light would turn red and then disappear. I checked my brake fluid and it is very very full (past maximum). I need to drain some of it out and I assume this is what the problem is, again not a big deal. However today something else happened. I was in stop and go traffic and my battery light came on very briefly then disapeared. I noticed that my car wasnt holding the idle great either. Then once again the brake, asc and abs light came on briefly, then the tire pressure sensor came blinking, then the red brake light came on, all while my car not being able to keep a good idle. I kept the revs up a bit in this stop and go traffic to see if it would go away. Then the speedo and tachometer froze ... Then 10 seconds later, everything went back to normal and the car is running great again. Now I really wonder what the h*** is going on. Is my battery failing ? My alternator going ? What's your take on this ? |
09-22-2016, 12:20 PM | #2 |
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Before you do anything else, get the codes read so that you properly diagnose the issue.
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09-22-2016, 12:48 PM | #5 |
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All manner of crazy stuff like this will happen when your battery reaches end-of-life.
If your battery is more than 4 years old, I would start with replacing it, regardless of what codes it has. My battery died recently and I got a similar Xmas tree of lights. Codes said throttle position sensors were bad. Luckily, there was another thread where somebody replaced their TPSs due to the same symptoms, but still had the problem. They replaced the battery and the problem went away, so I did that first.
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12-06-2016, 05:51 PM | #7 |
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Alright, I come back a little while later. So I changed my battery because the problem was getting worse and the battery was dying. I took it to a shop to test the charging system though and everything looked fine. Alternator churns 14.2V without load, and 14.1V under load, voltage regulator does it's job.
However, the issue is not fixed. I notice sometimes that the car will not hold idle perfectly. It is hard to notice but here is how I know something is wrong. In neutral, if I rev it up to 2k and release the gas pedal, it doesnt go back to idle, it'll go lower and struggle for a sec to get back to idle. Other dead giveaway is to get the car going in first gear and let it crawl on idle, it will not hold idle and almost stall. When that happens, I stop the car and restart again and it feels fine then. Now yesterday something else happened. I had the ABS, ASC and Red brake light come on and off when cruising in the city. It would come on for one sec, disappear for 3 sec, come back on etc. I parked the car and did some testing. In neutral at idle, it would not do it. If I pushed the gas, when reaching 2k rpm, lights would come on and I'd see my headlights flickering. I stopped the car, let it cool down till this morning and today everything is fine again. The shop told me my alternator was fine based on the test they ran. However I feel like there is some kind of loose connection between my alternator and the main circuit of the car that just comes on and off for some reason. This would be what killed my battery by the car switching to battery power when the connection would be bad and draining it. I believe maybe that is what happened yesterday night, battery couldn't supply enough power to the whole car when the car was not seeing the alternator power. What do you guys think ? |
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12-06-2016, 06:05 PM | #8 |
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I would rig something so I could monitor the bus voltage while I drive to get some hard data.
Hopefully that will yield more clues.
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12-06-2016, 11:16 PM | #9 |
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I had some similar crazy things happening, and it turned out the battery I thought was good, and only replaced 10 months ago, was actually not so good. Just recently replaced it with an O'Reilly 48 AGM that holds a strong charge for days now. Also, you stated this: "Alternator churns 14.2V without load, and 14.1V under load, voltage regulator does it's job". My car reads 14.7 at idle and 14.4 while driving. Prior to the new battery it would read similar to your readings. I ruined a good battery this time last year when my alternator went bad, and it turns out the replacement put in by my indie shop, an Interstate, wasn't holding a charge well. I've spent an assload of money on batteries in the last 18 months, but I feel good about whats in the car now. The car was driven tonight for the first time in 4 days and prior to cranking it read 12.6 V. I'm a happy camper finally.
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12-07-2016, 10:37 AM | #10 | |
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Quote:
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12-07-2016, 11:36 AM | #11 |
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symptoms of alternator going out. I was experiencing same. replaced alternator and I'm good to go
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12-12-2016, 10:58 AM | #12 |
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Yup same here, my problem was the alternator
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12-12-2016, 08:16 PM | #14 |
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Start at post #10: http://www.zpost.com/forums/showthread.php?t=1297038
To summarize, start with replacing the voltage regulator before replacing the entire alternator. You're welcome Pretty safe to say this is a common issue and should be done as a preventative measure.
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12-15-2016, 05:06 PM | #16 |
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When I replaced mine, everywhere I found the alternator for sale was running around ~$700. I ended up finding it around $300 on carparts.com. I believe that was the website and it was OEM. Good luck!
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04-03-2017, 08:21 PM | #22 |
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Know this is resolved but wanted to add another data point for folks in the future. Had the exact same thing with the holy trinity of lights flashing and sudden but brief loss of power. Ended up replacing just the voltage regulator in my alternator and was right as rain again. Part ran about 30 bucks and took about half an hour to swap out.
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