hieuln

Hi guys,

I have the problem with the battery for a long time and recently I tried to figure out which component is faulty but I am still not sure so may need your help.


I don't have the issue of over night battery draining. Let's say if I charge the battery, the next days it works good even leaving overnight. But very often I can't start the engine with all lights goes on in the dashboard. I have to use the jumpstart helper to kick the engine on.


Those are the things I replaced and did already:

- I replaced the IBS by the new one from Hella last week.

- I replaced the voltage regulator last year (Valeo) but since then I still have this issue. Today I replaced the carbon brushes from the voltage regulator.

- I also tried to unplug the IBS.


However, as I notice, sometimes the alternator doesn't kick in especially after a long trip, then I turn off the engine and turn on again. I look over the hidden OBD menu and also measure by multimeter, the voltage is well below 12V. Today, after about 30 minutes of driving, I stop, turned off and on again, the voltage slowly decrease from 12.5V until about 10V (in about 2 - 3 minutes), then suddenly the engine "wakes up" by a hiccup, the voltage raise up to 14V and stay there.


The other day I also notice, after turn on the engine, the voltage is about 11.6 - 11.7V for about 5 minutes then it raise to 14V and stay there for the whole trip (45 mins). Sometimes, when turn on the engine after the battery is dead, I have to use a jump-start to kick the engine on, the voltage is up to 14V right after 2 - 3 seconds.


Could that be a faulty DME? Of course, in INPA shows some error about BSD bit is missing and so on, but as I said, even when I unplug the IBS when the voltage (with engine on) is 11.5V or so, the alternator still doesn't kick in. I left the IBS unplugged for a month or so already, the situation is exactly similar.


Or should I replace the whole generator? Do you have any ideas? Thanks a lot for your help.

Best,

​​​​​​​Hieu

seanjordan20

I would replace the alternator. The DME has nothing to do with the voltage it's putting out

Redballs1

I have had an identical problem as you describe, there was a problem with the main battery positive cable that runs along the underside of the car. I was able to prove my theory by joining two jump start cables together and clipping one end direct to the battery and the other end onto the jumpstart point under the bonnet, i was able to repair the cable which was heavily corroded just above the rear axle. I only found this after replacing the battery, starter motor and alternator.

hieuln

I thought the DME is the one which decides how much voltage the alternator would output?

@Redballs1 Thank you very much for the hint, I'll try to have a look under the car tomorrow to see if this is the case, maybe I can test it as well by using 2 jumpstart cables like you did. If this is really the case, it would be an horrible problem ever because I tried so many ways and still can't understand why.

Redballs1

E60’s were subject to a recall for the joint in the cable where the cable goes through the boot floor. Mine had beeb recalled but the problem was further down the cable on the underside of the car. You should also check the earth cable from the engine to the body. This is on the right hand engine mount. Again you can prove or disprove by clping a jumper cable from the engine to the bodywork.

hieuln

Actually when I measured the voltage, I measured it at the jumpstart point under the hood which showed the same value as in the hidden OBD. Could that still be the case? Of course I will try to connect from the jumpstart point under the hood to the positive lead of the battery tomorrow to see if that's really the issue. I saw the post about the joint under the boot floor already, I can't check it right now but I would assume there is no issue there as I don't receive the recall letter for this. I got the recall letter about water in the trunk instead.

​​​​​​
You meant from the engine or from the alternator?

hieuln

Actually when I measured the voltage, I measured it at the jumpstart point under the hood which showed the same value as in the hidden OBD. Could that still be the case? Of course I will try to connect from the positive lead of the battery to the jumpstart point under the hood tomorrow to see if that's really the issue. I saw the post about the joint under the boot floor already, I can't check it right now but I would assume there is no issue there as I don't receive the recall letter for this. I got the recall letter about water in the trunk instead.


You meant from the engine or from the alternator?

Redballs1

In my case the cable would sometimes have connection and other times did not, when there was no connection there would appear to be no fault as the ancillary systems were fed direct from the battery to the fusebox in the boot however the starter motor and alternator are connected to the main cable that runs the length of the car, if connection was lost then obviously the starter wouldn’t run and also the alternator had no connection to the battery so would switch off, however the systems fed direct from the battery would still show a voltage hence less than 12v but still running, this slowly depletes the battery so even when the main cable does connect, battery condition is poor. Charging voltage was up and down. Post repair a voltage gauge plugged into the cigar lighter shows consistent 14.4v always. It doesn’t matter where you clip the earth lead as the alternator is earthed to the engine in any case. Faulty earth lead or faulty main cable can give the same fault.

hieuln

In your case I would expect that if you measure the voltage under the hood, it would shows 14.4v constantly. Because IBS will report the battery state is poor, then DME will tell the alternator to run at max (14.4v) to re-charge the battery. Of course it can't charge because the cable is broken. However, it was not like that so that theory is wrong. This is illogic for me somehow so definitely it worths to check the cable tomorrow. Thanks.

seanjordan20

Always test the alternator under the hood. That is the only way to tell if it's good or not. If you are testing it from anywhere else it's the wrong thing to do. Troubleshoot from the source back to eliminate. Never start in the middle because you will find yourself getting a false positive or negative.