E39 electrical problem

[bene36e39]

Our 1998 E39 528i has been having electrical issues. First time it happened it looked like a drained battery problem, however, it's not.

The car would run fine, until you park it. Then when you want to start the engine next day or few moments later, the car is completely dead - sounds like bad battery that wouldn't charge or a bad alternator.

Jump start would NOT help starting the car, you would hear the starter click once, but no more than that With a jumper-cable attached, the car has all the power, but it just wouldn't start - now it sounds like a bad starter. But when you remove the cable, there's absolutely nothing in the battery - now it sounds like bad battery / alternator again.

But the funny thing is, when you come back later, the car can be back as normal.

Today the wife also noticed that occasionally when the AC is on with moderate blower speed with the CD player playing, the power supply "flickered," - now it sounds like a bad voltage regulator? After she parked the car in the garage, the car went "dead" again, so dead, not even the steering colume moves up after you pull out the key. I went in the garage to check it out, everything was normal again. I tried to duplicate the problem by turning on AC and radio and driving light all together, nothing happened. I was able to start the car up.

I suspect that the voltage regulator is crapping out, but I'd like to hear what you guys think.

So voltage regulator? alternator? battery? starter? bad DME/program?

[bene36e39]

Took the E39 for an electrical system check this morning.

At 8:05 AM (after a drive from my house to a local shop)-
- battery charges fine (12.49V, 786/850CCA).
- alternator checks out fine
- starter checks out fine (cranking AMP is low,but ok voltage to start).

At 8:42 AM (now the interesting part) -
- battery status (12.36V, 726/850CCA).
- battery is good, but low on charge.

The battery is obviously capable of being fully charged, however, in less than 45 minutes, the battery status changed from "Good" to "Recharge." Something is draining it at an abnormal rate. The car either has excessive power drains or wiring issues (readings from Bosche BAT151 reader).

Alternator output reading is normal, and even though the starter is getting old, it's not the cause of the problem at this point.

Thoughts?

[jda2000]

The final stage resistor (FSR) is acting up. A common failure on these cars and the most likely reason the battery is dead.

[bene36e39]

The final stage resistor (FSR) is acting up. A common failure on these cars and the most likely reason the battery is dead.

Is it easy to swap? Any write-up or BMW part number? Any help is appreciated.

[ViolinARC]

Could be a bad ground on the FSR or something else. I have been told that bad grounds on some models can cause these issues intermittently and that would explain the intermittent nature of the problem...GL!

[bene36e39]

I have done quite a few FSR's on E36's, but never an E39, luckly, the procedures look very similer. I really hope that it's jsut a bad ground of the FSR; the new part is the on its way.

By the way, how do you detect a bad ground if it's omething else (cables, wirings, etc.)?

[ViolinARC]

I have done quite a few FSR's on E36's, but never an E39, luckly, the procedures look very similer. I really hope that it's jsut a bad ground of the FSR; the new part is the on its way.

By the way, how do you detect a bad ground if it's omething else (cables, wirings, etc.)?

Tough one since the ground problem will be intermittent. An ohm meter or try the trusty old "tap" test.... The "tap" test found my speedometer short on the 750...it was in the cluster!

[thejlevie]

What is the system voltage with the car idling and at 2500rpm. It should be at least 13.5v at idle and 14.0v at 2500rpm. If you aren't seeing that the alternator is probably the cause.

[bene36e39]

Follow up - thanks for all your input, the Final Stage Unit seems to take care of the problem. The installation was easy, took me only 12 minutes in-and-out.

[00BMW540i6]

Follow up - thanks for all your input, the Final Stage Unit seems to take care of the problem. The installation was easy, took me only 12 minutes in-and-out.

Easy replacement glad to hear it

[jda2000]

Follow up - thanks for all your input, the Final Stage Unit seems to take care of the problem. The installation was easy, took me only 12 minutes in-and-out.

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