Red Battery symbol, then abs dsc please help

[lhordmclain]

I agree with the all the troubleshooting steps mentioned above by other owners.

For my case, it was my orig alternator bearings. replaced mine with Genuine RFMD BMW (by valeo) 140amp alternator (retail at ~$600+ no tax, I got for only ~$400 including tax ) and kept the old one for autopsy/fun experiments.

Some will recommend buy RMFD or new OEM alternator for even less money. Keep in your orig alternator specs 120amp or 140amp or xxxx amp, air cooled versus water cooled .

Some will recommend DIY or go to an automotive alternator rebuild shop - defective replaceable parts like the bearings, VR and etc - most economical way to get you back on the road...

Just adding my .2 cents:


- Alternator isn't charging the battery (most cases -> the alternator is intermittently failing)
* Check terminal connections / ground cables
* Check voltage while car is OFF - should be approximately 12 volts
* Check voltage while car is idling - should be approximately 14 volts
* Check voltage at battery terminals while car is revved up a little (maybe 3k-4k RPMs) - should still be approximately 14 volts.
* Turn on everything Radio, AC/Heater and etc - the works

- Broken or lose accessory belt
* Check belt tension and position
* Check idler pulley and tensioner pulley

- Faulty ignition switch (can cause flickering or solid red battery light)

[bcredliner]

I never have any intentions to ignore input or defend something just because. I have no problem admitting when I am wrong. And, in this case, I am wrong about how the system works. I do stand by the poor man's methods of troubleshooting.

I agree that we are more knowledgable about some aspects of a vehicle than others and certainly there are differences in how things work from one brand to another so it is never a good idea to universally apply how things work. In my case I was thinking only of an E53 because that is forum.

JFOJ, Regardless of certification, experience or day job, I think when one declares themselves an expert they begin to be less effective. I suggest you use your knowledge to respectfully explain how something works when someone disagrees without sarcasm. I can't compare this forum to others but I do know OPs get help here. The forum was doing fine before I joined and it will do fine when I am no longer a member--none of us are an exception.

[upallnight]

Originally Posted by Helihover

Funny how I asked this same question almost two years ago and you ALL were on the other side of the fence!!!! Terminators car stopped running while he was driving. The battery came loose. I told you guys that the car should have stayed running, yet everyone insisted "bmws" won't because there is too much "electrical stuff". I even offered to try this on my own X, but YOU, upallnight, got me so nervous to try it explaining that there are current spikes and what not that alternator can not correct so you would take a chance of damaging components. So which one is it? Will your BMW X5 run without a battery installed?

Well accoring to the "expert", he back up what I said.

Originally Posted by jfoj

The battery dampens and filters the alternator output.

One thing that most modern vehicles do is the DME/ECU can and will kill spark and fuel if the input Voltage gets too high to protect the DME/ECU and other modules in the car in the case of a high Voltage swing. Usually 17-19 Volts it the trip point for most vehicle. No idea the exact value for BMW and I am not interesting in finding out on any of my cars.

You can arc weld with 120-200 Amps and as mentioned it is not a wise test to disconnect the battery on a modern vehicle for testing. Without the battery as a static load and filter, the alternator can do some funny things. Even filtering out AC ripple that can high peak to peak Voltages.

[bcredliner]

Since the electrical system runs off the alternator how does the battery become a filter for spikes? And if the DME/ECU and other modules protect from spikes why is it such a bad thing to run the engine with only the alternator output if necessary for a short period of time? Rather than reference most vehicles I think we need to stick to what is true of a E53.

[upallnight]

Originally Posted by bcredliner

Since the electrical system runs off the alternator how does the battery become a filter for spikes? And if the DME/ECU and other modules protect from spikes why is it such a bad thing to run the engine with only the alternator output if necessary for a short period of time? Rather than reference most vehicles I think we need to stick to what is true of a E53.

I said that the car ran off both the battery and alternator not one or the other. As more electrical load is placed on the system, the regulator compares the voltage that the battery is putting out along with the voltage the alternator is putting out. It adjust the alternator voltage so the battery is always being charged.

[upallnight]

Originally Posted by StephenVA

NEVER remove a battery connection when the engine is running. You will not like the results of the surge damage when reconnecting it. Modules will fail, electrical components will go off the deep end. Can it be done and not have any issues? Yes, but why take the chance? THis "test" was a short cut way back in the 60's left over from post war vehicles with generators.

Loose power connections have shorted out more electrical components than anything else in history. (An assumption on my part. No actual data collected...)

Regarding a vehicle that dies when the battery is disconnected: A good electrical system SHOULD have kept it running. But who knows what failed at the same time as the disconnect? The Regulator? The main module? The ground wire? Who knows? Maybe the alternator/wiring was DEAD/shorted before the disconnect.....

What we are failing to take into consideration is not just the voltage but the amps draw when Terminator lost power to his X. He was running at night with all the lights on and if it was in the dead of winter he might have had the blower motor on for the heater and imaybe the rear window defroster.

I have driven a car with a bad alternator on a battery as long as any non essential electrical device were left off including the radio. When the alternator to my PORSCHE crap out on me, I brought a new battery but only drove during the daylight hours. I was able to make the 40 miles trip back home on just the battery.

[bcredliner]

Originally Posted by upallnight

I said that the car ran off both the battery and alternator not one or the other. As more electrical load is placed on the system, the regulator compares the voltage that the battery is putting out along with the voltage the alternator is putting out. It adjust the alternator voltage so the battery is always being charged.

I understand the alternator regulator adjusts the output to keep the battery changed and provide for electrical systems draw. That seems contrary to the battery is only used to start the engine and supply current to those things that the circuit is completed when the key is turned on. And, that once the engine starts the alternator is the source of current for all electrical systems.

[dabenthusiast]

Called AAA today driver came out, I said I want it towed home.
Driver said let me jump it its probably your alternator but if it starts you'll be able to make it home, I said I just want it towed. He said drive it around the corner if it workstill it'll be fine you'll make it.


So I left. Speedo abs hill decent all started going haywire.
Car started braking when driving at 50 MPH and dash all went out speedo dropped then I lost power to car and pulled over.

Tow truck ca.e towed it rest of the way home. I'll do test tomarow. It started to rain and has been a long day .

[bcredliner]

Originally Posted by StephenVA

NEVER remove a battery connection when the engine is running. You will not like the results of the surge damage when reconnecting it. Modules will fail, electrical components will go off the deep end. Can it be done and not have any issues? Yes, but why take the chance? THis "test" was a short cut way back in the 60's left over from post war vehicles with generators.

Loose power connections have shorted out more electrical components than anything else in history. (An assumption on my part. No actual data collected...)

Regarding a vehicle that dies when the battery is disconnected: A good electrical system SHOULD have kept it running. But who knows what failed at the same time as the disconnect? The Regulator? The main module? The ground wire? Who knows? Maybe the alternator/wiring was DEAD/shorted before the disconnect.....

You begin your post with Never in all caps and bold type and then you say it can be done without issues. Then you say it has ruined more electrical components than anything else in history followed by that is an assumption. Confusing again.

[upallnight]

Originally Posted by bcredliner

You begin your post with Never in all caps and bold type and then you say it can be done without issues. Then you say it has ruined more electrical components than anything else in history followed by that is an assumption. Confusing again.

Stephen VA stated that it's only an issue if you go and try to put the cable back on with the engine still running.