[Jayvpro]

Hello guys. Im new here and desperate lol

So i was hoping with all of your guys knowledge i can solve my problem

I own a 2007 e92 335i with 100k miles. I've never had any issues aside from the typical water pump, but recently i began getting the low battery light but, i would rev up the car and the light will go away. i have an aftermarket stereo with jb4 and i was looking at the V on the battery constantly.
When i was getting the low battery the V would drop under 12v but after a rev it will jump to 13+ and stay like that for the day.

So i replaced the voltage regulator with an OEM replacement (i made sure it was the right part for a 180 alternator) but when i was trying to plug the battery back on after the replacement i got a pretty big spark from the positive cable and no power at all in the car.
freaking out i checked V on the connections and i have no reading from the voltmeter. so i went ahead and drive to the stealer thinking i blew my positive terminal distributer box. I replaced it and nothing is working.

Here is where it gets tricky.

I unplugged the negative cable, leaving the positive connection plugged in and I used the voltmeter to check for voltage by touching the negative post on the battery (12+v) but as soon as i plug in the cable no reading.

so i thought. Hey its probably my ground so i did the process backwards by leaving the negative cable plugged in and unplugging the positive cable touching the negative cable to the positive post and i got the same reading (12+v)
i tried all this in 2 batteries



Now i went ahead and realized i have positive ground I touch anywhere in the body and i have current so idk what the heck.

Im so lost on what to do now. Do you guys think i have an issue with the IBS or BST cable?

Extra info:
All recalls done including B cable behind the fuse box, never had any issues before the battery sparking. car will turn on without any problem. i cant check codes because there is no power what so ever.

THANK YOU FOR READING AND YOUR REPLIES

[csquared013]

Bump

I'm doubting the IBS being the problem. Mine has gone bad twice but it just constantly leeches power when it's bad. I was still able to crank.

When you say absolutely no power im guessing you mean not enough to run diag without the car actually running?

If no one with more intimate knowledge of this gets back to you I'd say call the stealer and see if someone will give you some advice since they work on these things for a living. My dealer in Santa Fe knows I do most work myself but everyone is real cool about free troubleshooting tips as long as they don't have to actually put their hands on the car.

[Jayvpro]

Originally Posted by csquared013

Bump

I'm doubting the IBS being the problem. Mine has gone bad twice but it just constantly leeches power when it's bad. I was still able to crank.

When you say absolutely no power im guessing you mean not enough to run diag without the car actually running?

If no one with more intimate knowledge of this gets back to you I'd say call the stealer and see if someone will give you some advice since they work on these things for a living. My dealer in Santa Fe knows I do most work myself but everyone is real cool about free troubleshooting tips as long as they don't have to actually put their hands on the car.

Thanks for the reply

I actually have no power at all to the electronics nor in the battery terminals.
So if i plug in both cables to the battery i get no reading in the voltmeter like if there was a cable in between not completing the circuit :/
Fuses are fine cable behind the fuse box is fine i followed the cable from
The back to the fuse box and no damage. So im stuck lol.

I guess my next thing to do is check for continuity on each cable from BST all the way out :/

Yes i was thinking about calling them and see if they can help, my ontario dealership is pretty cool but we shall see lol.

[rick100]

Originally Posted by Jayvpro

Thanks for the reply

I actually have no power at all to the electronics nor in the battery terminals.
So if i plug in both cables to the battery i get no reading in the voltmeter like if there was a cable in between not completing the circuit :/
Fuses are fine cable behind the fuse box is fine i followed the cable from
The back to the fuse box and no damage. So im stuck lol.

I guess my next thing to do is check for continuity on each cable from BST all the way out :/

Yes i was thinking about calling them and see if they can help, my ontario dealership is pretty cool but we shall see lol.

you need some type of wiring diagram for the battery , even if it is for a simple ring out.

its odd that you are not getting voltage at the battery post under the hood.
You need a diagram to see how the trunk positive terminal is connected to the positive terminal under the hood. If there is not continuity then something in between broke ( fuse??) , without a diagram its hard to guess

[Emilime75]

Your description is a bit of a mess.

Please re-write the "where it gets tricky" part. It isn't clear as to what cables you're plugging/unplugging and which meter terminal leads you're using to measure for voltage and ground.

Also, please describe exactly what you were doing and what happened when you got the spark on the battery positive post.

[ctuna]

The first time I took off the battery clamp on the negative battery
terminal I did not get power back . It turned out I had not pushed
the clamp down far enough on the terminal before tightening it.

Use your volt meter follow the voltage start from the top to the battery
and check for voltage at all the plug on top of the battery distribution
block that are active for starters.

[Jayvpro]

Update

I connected the positive connection on the battery and left the ground unplugged and i have current to the fuse box, alternator and starter.

I checked this by connecting a long cable straight to the battery (-) terminal to the voltmeter and the positive prong on the voltmeter to all of the fuses.
I did this because if I plug both negative and positive cables I have no power in the car.

I'll be buying another negative terminal cable at the junkyard just in case to see if this solves my issue.

I will keep you all updated

[Marc81]

sounds like you jacked up the regulator install, if it was fine before touching the alternator. I'd go back to the alternator and recheck your connections.

[Emilime75]

How does your ground strap look between the engine and chassis on the driver's side? Take you meter and use that as your ground reference for your meter, do you get 12v to starter, alternator...?

[Jayvpro]

Update:

I replaced ground strap on the back of the trunk and still nothing it seems as if the battery wasnt grounded.

Still looking for any burned cables or anything that can pinpoint a short in wiring.

I will keep updating

[gbalthrop]

Originally Posted by Jayvpro

Update: I replaced ground strap on the back of the trunk and still nothing it seems as if the battery wasnt grounded. Still looking for any burned cables or anything that can pinpoint a short in wiring. I will keep updating

Originally Posted by Emilime75

Your description is a bit of a mess. Please re-write the "where it gets tricky" part. It isn't clear as to what cables you're plugging/unplugging and which meter terminal leads you're using to measure for voltage and ground. Also, please describe exactly what you were doing and what happened when you got the spark on the battery positive post.

I don't mean to contribute to your angst, but we (at least I ;-) can't help WITHOUT:
1) Specific description of Voltage Reading at SPECIFIC, IDENTIFIED Electrical System Locations, and
2) What you were doing & WHERE when you got "big spark from the positive cable".
3) WHAT "positive cable" are you describing? At the Alternator? At the Battery? Why would you disconnect the Battery POSITIVE Cable? Did you disconnect the Negative Terminal at the Battery? THAT is the proper procedure when you are working on something that has a B+, UN-switched Battery feed, such as the Alternator.

There are basically 4 places you need to measure Battery Voltage as the FIRST step in diagnosing your issue, starting with:
(0) Battery Posts. Measure voltage with Red Meter probe on (+) Battery Post, and Black Probe on (-) Battery Post. Attached is a page from BMW Training Manual on Voltage Supply, which shows three cables that supply power to vehicle:

(1) in Photo is "B+ to Starter & Alternator". Measure Voltage at Jumpstart Terminal under hood, with Red Meter Probe on B+ terminal exposed when Red plastic cap is removed, and Black Meter Probe on "hex-pin" or ground stud attached to chassis at Right Wing/Fender.

(4) in Photo is "B+ to Engine Electronics". This is the Voltage supply to the DME and the DME Main Relay. Test for 12V+ (in relation to Chassis Ground) by either "backprobing" the connector of Cable #4 where it attaches to the Rear Power Distribution Panel, or by removing the Cable connector and simply testing voltage of the Fusible Link Pin the Cable connects to.

(6) in Photo is "B+ to Junction Box. Notice the Large Red cable attaching to the Panel on the Inboard side. Just flip up the red plastic cover over the end of the cable to reveal a nut that secures that cable to the fusible link. Measure Voltage at that nut, in relation to Chassis Ground

NONE of these tests require Ignition ON or Key in Insert Compartment. If you do those 4 Voltage measurements and report your findings, we can suggest "Next Steps".

George

[Jayvpro]

Originally Posted by gbalthrop

I don't mean to contribute to your angst, but we (at least I ;-) can't help WITHOUT:
1) Specific description of Voltage Reading at SPECIFIC, IDENTIFIED Electrical System Locations, and
2) What you were doing & WHERE when you got "big spark from the positive cable".
3) WHAT "positive cable" are you describing? At the Alternator? At the Battery? Why would you disconnect the Battery POSITIVE Cable? Did you disconnect the Negative Terminal at the Battery? THAT is the proper procedure when you are working on something that has a B+, UN-switched Battery feed, such as the Alternator.

There are basically 4 places you need to measure Battery Voltage as the FIRST step in diagnosing your issue, starting with:
(0) Battery Posts. Measure voltage with Red Meter probe on (+) Battery Post, and Black Probe on (-) Battery Post. Attached is a page from BMW Training Manual on Voltage Supply, which shows three cables that supply power to vehicle:

(1) in Photo is "B+ to Starter & Alternator". Measure Voltage at Jumpstart Terminal under hood, with Red Meter Probe on B+ terminal exposed when Red plastic cap is removed, and Black Meter Probe on "hex-pin" or ground stud attached to chassis at Right Wing/Fender.

(4) in Photo is "B+ to Engine Electronics". This is the Voltage supply to the DME and the DME Main Relay. Test for 12V+ (in relation to Chassis Ground) by either "backprobing" the connector of Cable #4 where it attaches to the Rear Power Distribution Panel, or by removing the Cable connector and simply testing voltage of the Fusible Link Pin the Cable connects to.

(6) in Photo is "B+ to Junction Box. Notice the Large Red cable attaching to the Panel on the Inboard side. Just flip up the red plastic cover over the end of the cable to reveal a nut that secures that cable to the fusible link. Measure Voltage at that nut, in relation to Chassis Ground

NONE of these tests require Ignition ON or Key in Insert Compartment. If you do those 4 Voltage measurements and report your findings, we can suggest "Next Steps".

George

Thank you so much for all your knowledge and time to write to my issue. I appreciate everything you told me to help me solve this issue.

I understand my description of my issue isn't clear so I tried to fix this and explain a little more in this video I just recorded.

Thanks to everyone as well

[icon2015]

At the moment, your positive terminal is in short with your car chassis and when you connect the negative terminal to the car you complete the circuit; thus, draining your battery power.

Try to remove the Alternator positive terminal and check the voltage after connecting the car negative terminal to the battery.

[gbalthrop]

Originally Posted by Jayvpro

...I tried to fix this and explain a little more in this video I just recorded.

Originally Posted by icon2015

At the moment, your positive terminal is in short with your car chassis and when you connect the negative terminal to the car you complete the circuit; thus, draining your battery power. Try to remove the Alternator positive terminal and check the voltage after connecting the car negative terminal to the battery.

Sorry to see that you've taken so much of the car apart. Hope you can get it back together properly soon. My SWAG is that the problem is (or at least WAS in the beginning ;-) ONLY in the Alternator. The Alternator has "Diodes" which act as "Electrical Check Valves" to allow current to flow from the Alternator to the Battery to charge it, but they are SUPPOSED to prevent current from draining back into the alternator after engine shutdown, which would drain your battery if the Diodes fail.

As icon2015 states, your battery is being drained by a significant "Parasitic Drain". Apparently NOT a "Dead Short-circuit" which would cause sparks to fly everywhere when you connect the (-) Terminal to the Battery (you probably have "mild" sparking that you can hear & see -- be careful of ANY sparks at battery, as Hydrogen Gas from Battery can explode), but enough to drain a fully-charged battery reading ~ 12.6 V to less than 12.0V in 2 to 8 hours. If your battery was going flat to the point of starter NOT cranking, and everything was operating normally when engine was running, then the Alternator Diodes are the likely cause of that "Parasitic Draw".

Your HFT Multimeter is ALL you need to test the Alternator, although it looks like the wires are breaking at the probe connectors, so you may have to invest another $7 soon.

Remember the 3 wires going forward to the front of the car that we talked about, and that you tested in the video: (1) Large to the Jumpstart Terminal/ Alternator/ Starter; (2) Medium to JB Fuse Panel at glovebox; (3) Small to the VVT Relay & DME in the E-box. Since what we are expecting to find is a "partial short-to-ground" which drains your battery, the SAFEST way to test for that is by DISCONNECTING the battery entirely: first the Negative terminal and then the Positive Terminal. Then use your Multimeter on the Ohms/ Resistance Setting, to TEST for "Continuity to Ground" or Resistance/ Ohms in Relation to Ground. ALWAYS disconnect power supply/ Battery BEFORE testing for continuity to Ground. Simply disconnecting (-) Terminal is sufficient here.

If you haven't used Ohms readings before, test by selecting 2000 Ohms (~ "6:30 o'clock position" on Meter dial), turn on meter, and touch Black & Red Meter Probes together. Notice that you have a "1" reading = "infinite" resistance or open circuit when probes are NOT touching and "00.0" reading when probes touch each other (~ 0 Ohms resistance or closed circuit). We want to TEST each of the three Red wires Separately, for continuity to Ground. We expect to have VERY low resistance in the Large Red wire (1) going forward to the Jumpstart Terminal & Alternator, and higher resistance or Ohms reading in the other two.

Start by removing the three Red cables from the rear of the Power Distribution Panel, removing the nut for the Medium-sized cable that goes to the JB Fuse Panel and the two "Snap Connectors" for the other two (the small wire going to the IBS on the Negative Terminal being the third).

Test for "Continuity to Ground" or Resistance in Relation to Chassis Ground on EACH of the three Red Cables as follows, Starting with the Small Cable that goes to the VVT Relay/ DME:
1) With Meter Dial selecting 2000 Ohms as above and Meter Switch ON, place Red Meter Probe on metal end of disconnected cable, and Black Meter Probe on good Chassis Ground, such as the disconnected (-) Battery Cable.
2) Read & Record Ohms Resistance;
3) Repeat for Medium-sized cable that goes to JB Fuse Panel; Record Value
4) Repeat for LARGE cable that goes to Alternator (and Jumpstart/Starter); record value.

IF Large Cable has considerably LESS Ohms Resistance than the other two, disconnect BOTH the large Red cable at the Alternator (Do NOT reconnect (+) Battery Terminal until this is reconnected to known-good alternator OR properly insulated/ isolated so as NOT to contact Ground) and the small connector at the Voltage Regulator (BSD "Control" Connector). Keep the battery terminals DISCONNECTED from the battery posts and charge the battery at 6-Amp Rate for ~ 5 hours, disconnect charger, and test voltage at battery posts ~ 15 minutes after removing charger (waiting for "surface charge" to subside). Record Value.

Please let us know the results of those tests.

ANYONE know where the Diodes are in the Alternator? Are they incorporated in the Voltage Regulator? If NOT, can they be tested/ replaced separately? Since a Reman Alternator is ~ $400, it would be nice to know if there is a cheaper "fix".

Your tests of voltage at the four points suggested indicate that the battery has SOME voltage (~ 7V at the time of video) which of course is NOT sufficient to crank starter, light lights, power Control Modules, etc. HOWEVER each of the three wires to the front of the Car: 1) Jumpstart Terminal/Starter/Alternator; 2) JB Fuse Panel; 3) VVT Relay in E-box ALL have the same voltage as the battery posts, so your fusible links in the Rear Power Distribution Panel (Red thing on top of battery) are OK.

George

[Occ224]

Any update?