Hi,
let's try and resume what we have so far.
On restriction is, that my multimeter is a 5 Euro device - it reads systematically to low. I hope we can interpret the data anyhow.
First abstract the system as Supply-Side and Load-Side.
In the Battery Test <BatterieTest.png> the Load was high (starter) and the alternator did deliver. Thus we can suppose that the Ri (inner resistance) of the alternator is to be neglected. Supply side is ok. We can confirm this when I have a look at the Coupling Control Module and the cc solenoid valve. When I manually engage the valve from the
Multiecuscan, the voltage as seen from the CCM takes a drop from 12.315V (cf. <off.png>) to 12.189V (cf. <on.png>) while the reading on the battery pole (supply side) stays virtually unchanged (lacking somewhat behind, which physically is impossible, I attribute this to my high-end-measuring-equipment, that gives a somewhat to low reading). Thus there is all the work done on the load side, none on the supply side. That's the way it is supposed to be.
(NOTE: Voltages are low as I am working on a 82% loaded battery. Manual actuation is not available while the enginge is running, so I had to do this test battery backed. Don't let this trouble your sight for the underlying pattern!)
From this test <off.png> to <on.png> we can further deduce that there is a remarkable resistance in row to the payload (consisting of the CCM and the solenoid being in parallel). This is not the way it should be.
Same picture I get when I go through similar test for the ABS Controller and the corresponding 8 plus 4 valves and the pump. Repeatable net voltage drops around 0.15 to 0.25V per device.
Now imagine in the case of the 4x4 jumping in (1 solenoid), the ESC jumping in (quite a view of the 12 valves plus the pump) then the there will be some rise in current, hence this not negliable resistence in row will take a big part of the voltage.
Ah, yeah, and as we observe this pattern for several Control Units, it should be somewhere very early or very late in the wiring going up to the or coming from the supply side.
Besides that I was taking a motorway ride to confirm that the recharging voltage really goes up to (and somewhat above) the normal 14.4V. My max was 14.6V.
And something measurable which I could not capture is, that when engaging the coupling control solenoid, the voltage reading drops shortly to 11 and somewhat.
I managed to capture this effect only when driving. It is a curve and I really did hit the throttle. Here you see a voltage drop to 11.87V recorded. Given the fact, that it is a digitalized reading, the "real" minimum should even have been somewhat lower. Now imagine the ESC jumping in at that very moment, starting the ABS pump and engaging up to 2 release and 2 load valves simultaneously...
My opinion (I challenge you to put me wrong!) is, that:
1. Charge Control (the device on the negative pole) is to defensive, hence we only obtain a 82% load state. As the whole supply is really at its limits by design (remember, they where fored to withdrew even some early available configurations like "winter package" with "additional e-heating"), this leads to faults in heavy use situations.
2. There is a unwanted resistor in row, probably a bad ground connection. Any garagist should be able to easily identifie the root cause of this.
Thx for your contributions!
David