JerzyBoy973

JUST GOT MY CAR BACK FROM THE SHOP!!! AND IT STILL DIED!!!
So as I've posted in the other "car die" thread, my car quit on me about a week ago. My mechanic tested it and and found that the battery was on ly receiving about 10-11 volts while running until the car died. We changed the alternator and I picked it up yesterday. It was charging fully and test drove beautifully. Now last night after all of my other repair work was done I brought her home and headed out on the town. She died 30 mins into the night! This morning she started fine without being charged at all. Any ideas folks? (I'm going to check the running and resting voltage as soon as I dull this hangover a little)

JerzyBoy973

Okay scratch that. It only started because it still had juice from last night's jump. It's still not charging. I bought the $20 relay that is supposedly the culprit according to some other lengthy forum discussions. I'll post my results as soon as it comes in.

BimmerFan52

You?ll know more when some codes are read. Was the replacement alternator new? Some rebuilt alternators can give lots of problems.

After replacing the alternator do you know if the battery was charged using a battery charger or was the car was jumped and the alternator used to recharge the battery? Some alternators cannot charge a totally dead battery without overheating and failing (typically the windings overheat and insulation fails on the coil wire causing shorts turn to turn). They are designed for short term charging to keep the battery charge ?topped off?, not sustained full output for extended periods. In any case the alternator should be tested on an oscilloscope for correct output.

Did you get any dash warning light before the car died such as battery not charging? Once running, the alternator should have kept the car running if alternator voltage output was sufficient and the current was getting to the point of power distribution in the car (trunk near battery). If the engine was running when the car suddenly died then this may point to 1. intermittent alternator output, 2. a connection between the alternator and power distribution point that is vibrating loose or 3. a computer or module that is interrupting the connection.

I can?t tell from your post if you are a DIYer. Can you measure the output of the alternator with a multimeter? A cheap one is less than $10 and can measure the voltage to see if the alternator output changes during operation. Drive around, opening the hood and check it every 5-10 minutes. Or easier yet buy a voltmeter $15-20 that plugs into the cigarette lighter.

Check that all connections at the alternator are solid. Sometimes pins in connectors can be damaged or wires pulled half way out of pins when stressed by handling during replacement. Voltage measured directly at alternator can be good during idle but the connection can vibrate loose during driving.

After that check to insure all connections are solid at the jump start terminal under hood where battery harness, jumper terminal and alternator all come to one point.

DME relay is a good place to look next.

Then it starts to point to a fault in some computer or control module interrupting power during driving, an intermittent connection in the conducting path between the alternator and power distribution panel or an intermittent connection between power distribution and a computer or module. Here is where fault codes should be showing up.

Did the previous owner own the car before the accident that totaled the car or did he buy it after it was rebuilt (electrical problems only after reconstruction)? What area of the car was damaged? Did you ever get to see salvage photos? If not, you can try to google the VIN and see if it was auctioned, with photos online. Knowing where the damage was localized may lead you to examine and test certain harnesses for crushed or missing insulation, breaks in conductors or bad connections at terminals. Any idea where and how long the wreck sat before it was rebuilt? If modules and their connections were exposed to water it can be a real challenge to track down the gremlins (the equivalent of some of the problems caused by MPMs in trunks being exposed to liquids for even a short time as connections corrode and change resistances).

Best of luck and keep us posted.

JerzyBoy973

Thanks for the response. I didn't DIY the alternator, but it was replaced with a reman. unit (I'm pretty sure that even dealer parts are mostly reman. as well, I could be wrong). There is never any warning that the car is about to shut down other than the battery light coming on seconds before every single light on the dash lights up. The new alternator charges intermittently just like the replaced one did. So that's not the issue. Something is causing the alternator to cut output, the only thing I can think of is a faulty relay. The car was charged on a charger btw.

BimmerFan52

Dealers use brand new units. You can buy new or reman. from most of the parts supply houses.

You say the new alternator charges intermittently just like the old one did. What does charges intermittently mean? Are saying that it is not putting out a voltage all of the time? How do you know this?

I don't think the relay is your problem because I don't think it prevents the battery from charging. The bad relay just turns the car off when the internals of the relay overheat. Once the relay cools the car would start again.

chiefm3

Do some research on the Integrated Supply Module, PN 12527510638. I just replaced mine (07 550i) - as I was having random stalling, and on some occasions not being able to start the car. I guess this has been an issue on 7 series for a while. My local dealer had the part in stock, it was $110, and I was able to replace it in 20 minutes. It is located underneath the passenger side cabin filter (under the hood). I replaced mine yesterday morning, and no faults yet. I'm convinced!

BimmerFan52

Were you having any problems with battery charging, or was the car just dying?

JerzyBoy973

Yeah I've come to this conclusion as well. I just spent the day with the car metering everything with a multimeter, scanning the DME and monitoring live readings. We also played around with grounding. We got 14 volts for a period only when we used sets of jumper cables to ground the motor to the frame and alternator. So since the additional grounding seemed to get the voltage up we'll put it on the lift tomorrow once the car that's occupying it vacates. Hopefully it's simply a bad ground. My fingers are crossed, in all of our searching that was the only time we got above 14v.

BimmerFan52

I think you're on track. What kept bothering me was not only were you not charging the battery, but the car won't stay running on the alternator alone.
Floating grounds will create havoc in any electrical system.
Did good alternator output require both the engine and alternator be grounded? Did you try just the engine grounded or just the alternator grounded?

Check alternator ground wire connections and engine ground wire, which is to left of passenger strut tower when looking at engine. Follow it down to block and check the connection there also.

Once you can keep the alternator generating voltage you'll quickly know if you still have battery charging issues.

gwf545

There is a good chance that your remanufactured alternator is also bad. See my recent bad experience post here: https://5series.net/forums/topic/124...elts-replaced/

The integral regulator on the alternator will cause all sorts of problems if it is bad. The remanufacturer does not alway replace the regulator. The voltage will bounce all over the place and cause systems to behave badly or simply shut down. My remanufactured alternator was worse than the original in that regard.