Electronic undervoltage issues/bricking
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From: Iowa
2008 CL550, 2022 EQB 300, 2023 EQS 450 4Matic
Electronic undervoltage issues/bricking
I recently had some functions not working correctly, such as the trunk not closing, windows not working, etc. I put it on the scanner, and had numerous components reporting undervoltage. I took a look at the consumer battery, and found the OEM battery was manufactured in 01/2015--well past its retirement age. So, I got a new battery. But the same electronic errors were still happening. I got another battery--same thing. Twice now, I've gone out to the garage to get in/start my car, and it has been completely bricked--the key fob does not open the door, no lights, nothing. I've used the manual key to get in. I hit start, and it fires right up like everything is just fine. Any ideas as to what might be going on? Bad alternator? Another clue is my driver door soft close recently stopped working. I don't see anything noteworthy when hooked up to Xentry. It is a 2008.
Last edited by nath_h; May 23, 2023 at 07:39 AM.
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2007 S600, 2007 Chrysler 300 SRT8, 2000 C5 Corvette, 2017 Mustang GT, 2023 300C, and a 2019 Lincoln
Can you check voltage both pre-start and post-start. Voltage should be 11.9 volts or higher at rest pre-start. After start, it should read about 14 volts and climb as it charges to about 14.5 volts. My hunch is your alternator is not putting out enough and that is killing your consumer battery slowly. Keep us posted.
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S500
I recently had some functions not working correctly, such as the trunk not closing, windows not working, etc. I put it on the scanner, and had numerous components reporting undervoltage. I took a look at the consumer battery, and found the OEM battery was manufactured in 01/2015--well past its retirement age. So, I got a new battery. But the same electronic errors were still happening. I got another battery--same thing. Twice now, I've gone out to the garage to get in/start my car, and it has been completely bricked--the key fob does not open the door, no lights, nothing. I've used the manual key to get in. I hit start, and it fires right up like everything is just fine. Any ideas as to what might be going on? Bad alternator? Another clue is my driver door soft close recently stopped working. I don't see anything noteworthy when hooked up to Xentry. It is a 2008.
the cars eat 37 amps with the key turned on engine off - so if you leave the key on to listen to the radio it will kill any battery dead in less than an hour - as the cars age the way it burns electricity seems to increase and a new battery will get funny in 20 minutes
even taking the key out and never leaving a door open and just driving the car - if its not used for 2 weeks 50% of the batteries grunt will have gone walkabout - leave it three weeks and it will throw error messages to itself - but on dual battery cars it will start
all cars are heading this way - but the 221 seems to have the most need to waste volts
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S500
bricked is NOT a phase you can correctly describe a low volt battery
bricked means it has become as useful as a brick - as in NOTHING can get it to function ever again
if you can charge it, it was just low volts ... keep doing it on a long term basis and you'll head towards damaging the battery and shortening it life span - that's not bricked
sounds more like a module is staying awake
bricked means it has become as useful as a brick - as in NOTHING can get it to function ever again
if you can charge it, it was just low volts ... keep doing it on a long term basis and you'll head towards damaging the battery and shortening it life span - that's not bricked
sounds more like a module is staying awake
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If his alternator checks out good then he probably has a parasitic drain as you suggest.
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Thanks everyone....good information. I'll check the voltage today. I've not done this before, but will watch a Youtube video to see how to do it correctly. Before this car, I've never had to mess around with electronics, so know almost nothing about it.
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Most cheap scanners will read voltage through the diagnostic port. It is much easier than using a voltmeter and climbing in and out of the trunk to get to the big consumer battery. You already know the starter battery up front is good since the car started after you got in with the hard key.
Keep us posted and good luck!
Keep us posted and good luck!
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From: Iowa
2008 CL550, 2022 EQB 300, 2023 EQS 450 4Matic
Can you check voltage both pre-start and post-start. Voltage should be 11.9 volts or higher at rest pre-start. After start, it should read about 14 volts and climb as it charges to about 14.5 volts. My hunch is your alternator is not putting out enough and that is killing your consumer battery slowly. Keep us posted.
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I would say yes on first blush. IMO, she should be putting out about 14.5 volts and you are down a full volt which seems odd to me. How old is the alternator? Is it original? Here is a spec sheet from FCP Euro for a Bosch alternator and 14 volts. Note there were two alternators listed one for just under $400 and one for almost $1000. FCP is pretty good about allowing you to return unused parts.
I'd be partial to buying a new part and if it doesn't resolve your issues; I would send it right back. Of course, it is so easy for me to spend your money and time. But I do think your alternator is on the way out.
https://www.fcpeuro.com/products/mer...rnator-al0864x
Keep us posted.
I'd be partial to buying a new part and if it doesn't resolve your issues; I would send it right back. Of course, it is so easy for me to spend your money and time. But I do think your alternator is on the way out.
https://www.fcpeuro.com/products/mer...rnator-al0864x
Keep us posted.
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I would say yes on first blush. IMO, she should be putting out about 14.5 volts and you are down a full volt which seems odd to me. How old is the alternator? Is it original? Here is a spec sheet from FCP Euro for a Bosch alternator and 14 volts. Note there were two alternators listed one for just under $400 and one for almost $1000. FCP is pretty good about allowing you to return unused parts.
I'd be partial to buying a new part and if it doesn't resolve your issues; I would send it right back. Of course, it is so easy for me to spend your money and time. But I do think your alternator is on the way out.
https://www.fcpeuro.com/products/mer...rnator-al0864x
Keep us posted.
I'd be partial to buying a new part and if it doesn't resolve your issues; I would send it right back. Of course, it is so easy for me to spend your money and time. But I do think your alternator is on the way out.
https://www.fcpeuro.com/products/mer...rnator-al0864x
Keep us posted.
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Warranty is a great reason to let the dealer do it. I had a warranty for my first 4 years of ownership of the 2007 S600. I guess I spent about $12K over those four years and they reimbursed about $7500 (suspension, radiator, ABC, battery, water pump, etc). The warranty cost $5700 when I bought the car so I did pretty well. Remember a warranty is a risk sharing plan not a replacement plan. They always try to weasel on something. My favorite was the right front control arm replacement and they would only reimburse for half of an alignment.
You could have both a failing alternator and a parasitic drain. In fact, a bad enough drain for long enough could actually kill an alternator. I had an old Plymouth and the floor mounted bright lights button grounded out to the unibody frame and caused me to kill three batteries and three alternators before they discovered the problem. And that was when a battery was $39 and an alternator was $100.
Keep us posted on the outcome.
You could have both a failing alternator and a parasitic drain. In fact, a bad enough drain for long enough could actually kill an alternator. I had an old Plymouth and the floor mounted bright lights button grounded out to the unibody frame and caused me to kill three batteries and three alternators before they discovered the problem. And that was when a battery was $39 and an alternator was $100.
Keep us posted on the outcome.
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1983 Nissan Shltbox
reboot the car!
can't we get into the service menu and check voltage like in the W212?
New battery is fine, obviously, but the alternator is smart, so you won't get a 14.5V constant charging sine wave. To do that, you have to disconnect the LIN line plugged into the alt. There is an extensive thread on this in the 212 section.
Point is, charging voltage will vary based on ECU logic.
can't we get into the service menu and check voltage like in the W212?
New battery is fine, obviously, but the alternator is smart, so you won't get a 14.5V constant charging sine wave. To do that, you have to disconnect the LIN line plugged into the alt. There is an extensive thread on this in the 212 section.
Point is, charging voltage will vary based on ECU logic.
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there should be a secret menu on the cluster that will show volts - its all over youtube - and it will move about based on what it needs .... I thought 13.9v at idle is more normal.... but engine off it will soon drop lower than 12.5v - give is 20 mins and it will be howling towards 12.1v and 11.9v after 35 mins
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I believe DAS is all that would be needed for a component level check on the charging system.
For parasitic draw I use this Power Probe unit, saved hours, spendy but worth it IMO.
For parasitic draw I use this Power Probe unit, saved hours, spendy but worth it IMO.
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I sent my car off yesterday to have an interior issue fixed, but hopefully will have it back this weekend to play with it. I ran a battery check before I left yesterday. The battery went from 100% SOC to 64%, sitting overnight. So I'm thinking parasitic draw is highly likely. Maybe along with the alternator. Senecat, thanks for the ideas, but that's above my head...I'll ask BenzNinja about that one.
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Most cheap scanners will read voltage through the diagnostic port. It is much easier than using a voltmeter and climbing in and out of the trunk to get to the big consumer battery. You already know the starter battery up front is good since the car started after you got in with the hard key.
Keep us posted and good luck!
Keep us posted and good luck!
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From: Washington, DC
2007 S600, 2007 Chrysler 300 SRT8, 2000 C5 Corvette, 2017 Mustang GT, 2023 300C, and a 2019 Lincoln
Man that really sounds like a parasitic draw. There is a sensor or relay that is awake in error. I would set up that voltmeter or scanner to read voltage and pull each fuse one at a time until you see a big change in voltage. That will tell you which circuit. It could also be a SAM but I would think DAS would have told you about that.
If you can find the parasitic draw and it turns out to be a component stuck awake, you might avoid that alternator replacement. I would also comment that a 15 year old alternator is probably due and you have a warranty. I'd go for it anyway. I know; it is so easy for me to spend your money.
If you can find the parasitic draw and it turns out to be a component stuck awake, you might avoid that alternator replacement. I would also comment that a 15 year old alternator is probably due and you have a warranty. I'd go for it anyway. I know; it is so easy for me to spend your money.
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I can help. Pull off the long black plastic cover, next to the starter battery. The tallest post under that cover is the positive for the consumer battery. You can attach the negative to a bolt on the body.
