Charging system on 2003 Z4

[Shamrock20]

What I have Learned

I have been trying to get my
2003 BMW Z4 3.0 alternator working for almost a year. I purchased a replacement from Autozone - Duralast. It did not work. Autozone said it was probably something else like a loose connection. I read a lot of post and many had misinformation confusing newer models with the older Z4 from 2003 to 32006. I have learned that a lot of what I read is wrong or not applicable to this year.

I did learn this much:
1. There is no way to register the battery. I bought the BMW DIS V57 Diagnostic program and head unit. There is no way in the program to register the battery on an E86. This did not start until after the 2006 model year.
2. There is no Intelligent Battery Sensor (IBS) on the ground cable. This was not used until after 2006.
3. The DME does control the charging.
4. The default for the alternator is to charge if you unplug the control cable.

This is important to determine if the alternator is the problem or if it is the DME control.
I unplugged the control cable and the alternator did the same as if it was plugged in. When it
reached operating temperature the alternator cutout. I called Bosch technical
service and they said it was probably the regulator.

I also learned that when someone like AutoZone - Duralast rebuilds alternators they do not replace
the regulator. They do replace the brushes in the regulator. They do test them but probably not as long as necessary to have
the fault show up. It takes 15 to 20 minutes at operating temp to have the
alternator cut out.

A new regulator is almost the same price as the rebuilt alternator. I
t could be that the regulator not working is is why the alternator was turned in as a core
deposit in the first place.

I am now going to replace the regulator and see if that fixex it. I will post the results.

[Shipkiller]

What I have Learned

.......the battery on an E86. This did not start until after the 2006 model year.
.......Intelligent Battery Sensor (IBS) on the ground cable. This was not used until after 2006.

Just to make sure no one gets confused, yes BMW started most of what you have stated on most models of vehicles in 2006.
The E85 and E86's did not get updated with this newer technology....

Just to reiterate, NO BMW Z4's (E85/E86) from 2003 to end of production in 2008 have battery registration...


Something to help you out.....

Alternator voltage regulator

The rectified voltage generated by the alternator depends on the electrical load and the engine speed. A regulator system is required in order to supply the electrical loads with a constant voltage. The alternator voltage is normally controlled to values between 13.5 V and 14.5 V. Large changes in the current load of the alternator (major loads cutting in or out) can cause the voltage to temporary deviate from this range. These swings, however, must not exceed 1 s.

Battery charge indicator lamp

Terminal D+ is replaced by an isolated electronic terminal 61E in alternators with a multifunction controller. The task of this terminal is, on the one hand, to activate the battery charge indicator lamp and, on the other hand, to indicate to the various loads that the alternator is in charge mode.

The battery charge indicator lamp itself is supplied via terminal 15 from the instrument cluster. It comes on when the voltage at terminal 61E is below 1.5 V. The battery charge indicator lamp goes out when the voltage at terminal 61E is above 8 V.

Alternators with a multifunction controller can be recognized by the plug connection of terminal 61E. As a result, the 6 mm threaded stud has been dispensed with.

The indicator lamp lights up when:
Ignition on with engine stationary, alternator does not charge, failure of belt drive, interruption in excitation, controller overvoltage, break in charging cable
The second cable in the plug connection at the alternator is terminal 15 that serves as a reference signal for determining whether the alternator is charging.

Load Response Function, Alternator Voltage Regulator

The alternator current changes abruptly by switching major loads. This load results in engine speed fluctuations when the engine is running at idle speed or at low speeds. In order to prevent this disturbance the load response function of the alternator limits the power increase at low engine speeds as engine operation is particularly susceptible to disturbances at these low speeds. The current increases at a rate of approx. 10 A per second at engine speeds below 1000 rpm. An unavoidable side effect of this function is fluctuations in the brightness of the headlights at idle speed.

The load response function is not active at medium and high engine speeds.

Fluctuations in the brightness of the headlights at engine speeds above 1000 rpm are an indication of a faulty voltage regulator.

Start Load Response Function

The start load response function prevents the alternator already supplying current during the engine start procedure. This results in a slight mechanical resistance for the starter ensuring improved starting characteristics particularly at low temperatures. .

The start load response function prevents the alternator generating current for up to 2 s after starting the engine. As a result the alternator current increases at a rate of approx. 10 Amps per second.

The starting characteristics can be severely impaired if the start load response function fails.

[Shamrock1987]

My 2003 Z4 3.0 only has one light blue wire on the connector to the voltage regulator. I assume the alternator is internally energized.

Many of the forums say there are two wires and there are two pins, one is blank. I think that the blank is for a energizer connection and the blue wire is for the battery light.

Can anyone shed some light on this?

My alternator charges at 14.6 volts for a while but when the engine warms up after about 30 minutes it quits charging except for short burst of 14.6 volts. Mostly the voltage is 12.3 or below.

[Shamrock1987]

I did find a schematic in my Chilton's BMW 3-Series/Z4 1999 - 2005 Manual that shows there is only one wire connected to the regulator. It is a signal wire for the battery alert on the instrument cluster.
There is no second wire that is shown on many post related to this model Z4.

All front engine wires go through a connector box on the left side of the engine so there is no easy way to trace the connection.

The problem I am having is a long time problem. I have replaced the alternator, then the Regulator and it worked for several years but now is back to the same old problem. I think a new regulator is the answer but will wait to see the advise of others first.

[MIKYZZ4]

Your missing part of the equation, also have the battery tested.

[MIKYZZ4]

If you find you need to replace the alternator/regulator, I would search for a salvage yard BMW O.E. unit before gambling on AutoZone trash, as you seem to have found out.