complete power loss

[mister1k]

really need some help on this one 92 525i ,a little history I had alternator rebuilt 6 months ago,I have a huge intersate battery good and fully charged.3 weeks ago I get in the bimmer after work I have a 60 mile trip one way.It is minus 30 celsius outside,I have remote starter so i start car 5 minutes before shift end.no problems ,get in car turn on the heat,rear defog etc,start heading home.I go about 30-40 miles,I notice my wipers really running slow,and i swear my lights are getting dimmer,then things start happening,ABS light comes on ,then check engine,then trans program,then tach dies,lights getting dimmer, car starting to run rough.I am lodssing all power all system shutting down systematically,pull off the exprees to a mini mart,theres a cop in the parking lot.Shut the car down before i kill the battery totally,because obviously my alternator doesn't seem to be working.to to start car couple of turns but she is prettywell dead.I ask the cop to call me a tow truck,have a smoke,check my battery connections alternaotr belts,fuses anything i can think of.this was a bout 20 minutes in total. I decide to try and start car one more time see if battery has gained a little recharge.voila Car turns over slowly but has enough to fire up,ALL SYSTEMS GO,everything back to normal.full lights fast wipers no messages,I cancel tow truck,get in car and drive home the last 20 -30 miles,get home shut off car wait 30 seconds and start car no problem.Very puzzled.Next morning throw battery charger on for 4 hours battery fully charged.take off to work daylight now,get about 30-40 miles ,it starts all over again abs light first,check engine,trans program,tach,I gotta get off the highway.I dont have time to piss around I have to get to work,new job cant be late, third day.Brother in law picks me up takes me to work,and has my car towed to BUDDS BMW Oakville,Ontario Canada.They have the car for four days,cost me 1400 dollars for car rentals ,two tail light assemblies ,some dash lights ,and labour and trouble shooting for power loss problem.THEY say Alternator good,battery good,they took car out for two 45 minute runs.Tell me everything checks out.AT NO TIME DURING THE LAST FEW DAYS DOES THE ALTERNATOR LIGHT EVER COME ON WHEN THERE IS POWER LOSS.IT COMES ON NORMAL AT STARTUP THEN GOES OFF. I have car back for five days,no problem,then yesterday on the way home from work exactly same scenario,40 minutes into the drive complete power loss,stuck on side of road,wait 30 minutes for battery to gain little charge,just enough to start car and drive home.everything running again and i can definately hear alternator whine,seems like just not all the time.Anyone have any ideas,are there any modules,i can check,where is General MODULE????????1992 e34 525i 170,000 km,Very strong car.thankx in advance for any ideas or tests I can perform.

[Martin in Bellevue]

Maybe the fusible link is cracked? The fusible link is near the battery connection. After a load & some heat, they connection is going to crap.

[Javier]

problem, it is clear that the system is not charging the battery (nor supplying power to the car) but as soon as you let it cool a bit, it works fine, probably until it gets hot again. To re-produce the problem, the shop should have the car around 45 minutes in generator full charge, probably lights, wipers, heater, radio, window defogger, interior lights, ..... what ever to put heavy load to the generator. You should be able to do it at home, running engine, full generator load turning on every possible device.

I posted a picture showing the charging system in the interesting area. If you have no battery light alarm, it means alternator didn't stop working, it is confirmed if window defogger and climate control did not stop working. Unfortunately, the generator can be pushing power, but if full bridge rectifier (6 power diodes) or the connections are bad, power is not getting out to the electric system.

In the picture, I remarked in red circles what I feel may be wrong. Either, internally in the generator, the full bridge rectifier is opening wile hot (the connection to ground for example, or to the + post), or the external wires from generator to the starter motor have loose or dirty connections, generating a hot spot wile under load, thus increasing its resistance and deteriorating the charging ratings.

Check for the connections first, should be clean and tight, then start the engine, load the generator, all lights, heater, defogger, hook a voltmeter between generator external + post and the B+ post inside the E Box (The box at the engine compartment right corner containing the ECU), you should have a slight voltage drop there, if it increases when you notice things are going bad, or fall to no voltage drop at all, you have identified the fault. An increase means the external connections are bad, sudden no drop at all will mean you have internal open circuit at the alternator.

Javier

[mister1k]

thankx for input Javier and all

[632 Regal]

What did you rent man?

cost me 1400 dollars for car rentals

I agree its the alternater/regulator. Get a new one, sometimes the rebuilt ones are worse than the old ones.

[mister1k]

i disconnected everything ,GM,all unions from alternator,(union up front)cleaned,inspected.I drove car for two days now after cleaning and inspecting,I constantly run test 09 on OBD,I am getting 13.5 -14.2 volts underload and no load,Car seems to be running flawlessly but now power sunroof opens but does not close,minor compared to whats been going on,I think that is a general module issue ,I am going to try reset on sunroof today.With all that has been going on this issue is minor.Mister

[DanDombrowski]

Thats like $3.50 American Jeff....

I'm sorry, it was there. No offense to Canadians or the exchange rate.

[632 Regal]

dan, your 525 did 15.6 @89.9 MPH? Thats pretty respectable!