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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 03-07-2012, 04:31 PM
GK528i GK528i is offline
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Mein Auto: 98 528i, 04 330xi
Stupid battery light

Anyone ever experience their battery light coming on for no logical reason?
Mine keeps coming on and going off at random times and I can't figure out why.
This all started with the top hose blowing off of the radiator. This ultimately resulted in a cracked head. I replaced the radiator, water pump, battery and had the alternator rebuilt. I had an indy shop do the head replacement. Ever since I got the car back about a month ago the battery light keeps coming on. I have checked the voltage in the cluster read out (13.6) and have checked the voltage coming directly off the alternator. I took the car back to the shop and they spent a day testing and could not come up with a reason. Car starts fine and is charging and I have no other issues except for the battery light. I can not make it come on or go off. I've tried turning everything on in order to load the system and can't force the light to come on. I've driven at night with lights, seats and steering wheel all turned on and all is fine. The alternator shop said they would test the alternator if I brought it back in. Of course this means I have to remove it. Not a big deal but a bit of a pain. I have checked and cleaned the two wire connector on the back of the alternator. It appears that one of those wires is the voltage report to the computer. Battery connections are tight. I have driven on rough roads to try to make the light come on or go off to no avail. I realize that sometimes new parts can be bad so maybe the regulator unit that was installed is the problem.

Any ideas or suggestions in solving this would be greatly appreciated.
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  #2  
Old 03-07-2012, 04:39 PM
edjack edjack is offline
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Check the engine ground strap to make sure it's clean and tight.

Does the cluster voltage remain steady when the light comes on?
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Last edited by edjack; 03-07-2012 at 04:42 PM.
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  #3  
Old 03-07-2012, 04:52 PM
GK528i GK528i is offline
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I can see no change in the voltage no matter if the light is off or on. I have monitored the cluster voltage when the light has actually come on and do not see a fluctuation. Do you know where the ground strap is off hand. I have not checked it yet. Would it have been removed for the head work?
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  #4  
Old 03-07-2012, 07:05 PM
edjack edjack is offline
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On the V8, it's on the bottom of the block, a heavy cable between the engine and the support cradle. Don't know about the six, and it would not have been disturbed, methinks.
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  #5  
Old 03-07-2012, 07:39 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by edjack View Post
On the V8, it's on the bottom of the block, a heavy cable between the engine and the support cradle. Don't know about the six, and it would not have been disturbed, methinks.
I looked in here for 'ground strap':
- DIY how to test a BMW E39 battery & alternator

But there were no pictures of said strap ... so ... when you find it ... if you can post a picture in that thread, it would help others in the future not have to look for it like you have to.

EDIT: I found this in the bestlinks looking for "ground" but it seems to be for the DME:
- Electric Problem (Ground Wire) Fix DIY

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Note: Your mission, should you decide to accept it, is to add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need, in seconds!

Last edited by bluebee; 03-07-2012 at 07:47 PM.
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  #6  
Old 03-07-2012, 08:37 PM
GK528i GK528i is offline
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Thanks both Ed and Blue. I will certainly check the strap. I'm almost thinking the solution is going to be something odd like that and the computer is getting a false reading. If the strap is loose or not making good contact it actually would be a true reading though. I've also thought about disconnecting the battery cables but I'm sure the computer has a cmos battery. So is there any way to "reboot" the computer module?
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  #7  
Old 03-08-2012, 06:27 AM
jygesq jygesq is offline
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a reboot is very common to fix electrical glitches

Quote:
Originally Posted by GK528i View Post
Thanks both Ed and Blue. I will certainly check the strap. I'm almost thinking the solution is going to be something odd like that and the computer is getting a false reading. If the strap is loose or not making good contact it actually would be a true reading though. I've also thought about disconnecting the battery cables but I'm sure the computer has a cmos battery. So is there any way to "reboot" the computer module?
. Shut car off. Open trunk wait 16 minutes, trunk light will go off. open the battery
compartment. Disconnect the neg cable from battery. disconnect the positive cable. Short the cables together. Some people turn the ignition switch to position 2 while the cables are shorted. I usually just remove the neg cable from the battery , BE SURE CAR IS NO RUNNING. It is easy to do with no down side except you loose the trip milege information.
Nothiong to loose to try it.
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  #8  
Old 03-09-2012, 11:12 AM
GK528i GK528i is offline
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Checked ground straps and disconnected the battery, shorting the disconnected leads together. Battery light still on.
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  #9  
Old 03-09-2012, 03:46 PM
cn90 cn90 is online now
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In the back of the alternator, there is a rectangular connector.
I bet you money the mechanic (who replaced your alternator) forgot to reconnect rectangular connector.

Here is the picture showing the rectangular connector:


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  #10  
Old 03-09-2012, 06:53 PM
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moots moots is offline
wat's dat noise
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Quote:
Originally Posted by GK528i View Post
. I have checked and cleaned the two wire connector on the back of the alternator. It appears that one of those wires is the voltage report to the computer. .
well the op did that already.i had the same issue after i refitted my alternator.i re-seat that connector and fixed it.maybe the spade metal connector is loose inside?have someone wiggle the connector with the engine running and see if the light flickers....
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  #11  
Old 03-09-2012, 08:51 PM
GK528i GK528i is offline
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The rectangular plug is connected. If it was not connected I don't believe the light would ever turn off. I have tried unplugging and plugging the connector back in while the car is running and it still stays on.
I did notice this today. I have thought the light was dimmer than it should be when it comes on. In daylight it's sometimes a bit hard to see when it is on. So today while checking things at on point when i turned the key to the second position and all the lights (battery, oil etc) come on for the light check the battery light was as bright as all the others as it should be when i started the car the light remained off. Once the light came on, dimmer, and i turned the car off it was still dim at the 2nd position light check and remained on when i started the car.
I have cleaned the connector with cramolin. The spades on this connector are pretty small so I didn't have a brush to get down in them and scrub them. There are no signs of corrosion on the connector but after applying the cramolin i connected and disconnected the plug a few times to work the spades.
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  #12  
Old 03-10-2012, 08:27 AM
cn90 cn90 is online now
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if you have done all that stuff and still had the battery light on the dash, perhaps the new alternator is no good???
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  #13  
Old 03-10-2012, 09:11 AM
pleiades pleiades is offline
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Sure sounds like an alternator problem. GK528i, when you had the alternator rebuilt, did you make sure you got back the same unit with same brand (whether it's Bosch or Valeo, I'm told it needs to be the same brand that was in the car), voltage rating, and new regulator? Was the new regulator a BMW part or something aftermarket?
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  #14  
Old 03-10-2012, 02:09 PM
GK528i GK528i is offline
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Yes it its my same Valeo alternator. The shop has been in business for years. All they do is radiators and alternators. I have dealt with them for 15-20 years so I trust their work. That's not saying a new part could not be bad. They did not replace the bearings but did inspect and I respect their opinion. Only the voltage reg unit was replaced. I will have to find my repair ticket as I'm sure the manufacturer and part number is on it for the replacement part. I didn't have the time nor access to a bearing press when i had the unit rebuilt. At this point I am thinking about just ordering a new reg unit and replacing it myself just to rule that out.

Last edited by GK528i; 03-10-2012 at 02:10 PM.
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  #15  
Old 03-10-2012, 07:01 PM
crazy4trains crazy4trains is offline
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I took my Bosch 120 amp alternator to a reputable rebuilder several weeks ago. He bench tested it and said it was OK. I was skeptical but he tested it twice. I took it home and put it back on the car and put in a new battery. 2-3 miles from home and "Boom"; then transmission in failsafe mode. Battery light is also on. I take it home and check the alternator output. It is still poor. At that point I just bit the bullet and bought a new alternator. That solved the problem.

Maybe there is a feature ??? that permits these alternators to receive a good bench test but still be bad. If you have the spare change try a new alternator. That all I can offer.
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  #16  
Old 03-23-2012, 03:11 PM
GK528i GK528i is offline
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I was talking to a guy at an indy shop today about my battery light problem and he was telling met that there is a diode on the instrument cluster in the battery light circuit that may be causing the problem. Anyone have experience with this or better yet a diagram of what I may be looking for.
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  #17  
Old 02-09-2014, 01:33 PM
josemedeiros007 josemedeiros007 is offline
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Where should the Factory engine ground strap be located at on a 1998 E39 528i? My Google search's only turn up ground strap locations on other model BMW's.

My 2.8 Litre engine was replaced with a lower mileage engine due to my idler pulley and serpentine belt failing causing my radiator to blow a hole in it near the upper Radiator return hose from the overheated engine super heating the steam and also cracking the cylinder head.

Since then I have had electrical charging problems, I replaced the factory Valeo Alternator with a Autozone Bosch rebuilt after the engine change a year and a half ago, and again this past week with the same Symptoms, and I am wondering if this may be a ground related issue, and if the engine ground straps were reinstalled during the engine swap.

The Battery was replaced a year ago, it's a 72v month Interstate, they have checked the battery twice and charged it overnight, and thought it was my alternator not putting out a full charge. We both tested the voltage at the battery with the car running and it was at 13.5 volts with a digital volt meter, but then tested bad when the Autozone clerk brought out the load tester, and tested it on the car, he stated that it was only putting out 12.9 volts under a load.
http://www.vacmotorsports.com/catalo...s50-s52-us.htm

I see the interior lights pulsing / flickering at Idle, and the headlights dim when I press on the brake pedal, and or roll up the Windows and place a load on the Electrical system.

My previous Alternator was a Valeo with a three pin connector on the back, but the pulley was damaged during the engine install, and I could only find a Bosch pulley at FCP Euro, and the BMW salvage yards would only sell a Valeo style pulley with the used Alternator for $150.00 plus. The Autozone remanufactured Bosch alternator has only two pins, but accepts the factory BMW E39 three pin connector wiring.

Any suggestions would be appreciated, other then buying another BMW.

Jose F. Medeiros
408-256-0649 Google Voice
San Jose, California
http://www.linkedin.com/in/josemedeiros
"There is nothing you can't accomplish if you let another man take the idea". ..President Ronald Reagan

Last edited by josemedeiros007; 02-09-2014 at 01:42 PM.
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