Technical Alternator only starts generating after revving

[koalar]

0.5v while cranking?, most cars drop 3 or 4 volts while cranking.

Are you sure

Every car I have tested has been under 0.5V unless it has a faulty block ground

My panda has a 0.2V voltage drop battery negative to block

 

[nigelvan]

0.5v while cranking?, most cars drop 3 or 4 volts while cranking.

Voltage drop between negative terminal and engine block. You're probably talking about battery voltage drop when cranking.

 

[koalar]

@koalar yes that's correct.

If you jumper these two wires

At ignition on D+ would still be below 4.5V
At cranking the D+ would get battery feed
At engine running D+ would be normal output

Shouldn't throw a battery light error

Not ideal

 

[nigelvan]

If you jumper these two wires

View attachment 446355

At ignition on D+ would still be below 4.5V
At cranking the D+ would get battery feed
At engine running D+ would be normal output

Shouldn't throw a battery light error

Not ideal

this is the signal to the starter motor, with D+ at 14V this would keep the starter motor engaged...
Anyway, the problem is solved with the new Bosch regulator.

 

[koalar]

this is the signal to the starter motor, with D+ at 14V this would keep the starter motor engaged...
Anyway, the problem is solved with the new Bosch regulator.

You are correct, my mistake

Glad the new regulator fix it, what's that 3 regulators including the original

Well done in sticking with it

 

[vexorg]

Voltage drop between negative terminal and engine block. You're probably talking about battery voltage drop when cranking.

yes, sorry

 

[nigelvan]

You are correct, my mistake

Glad the new regulator fix it, what's that 3 regulators including the original

Well done in sticking with it

Yep, I did return the Hitachi regulator, hoping to get my money back. So then it was a 40 € fix.
It still slightly revs up when starting the van, but it does start the alternator on its own. I'll keep it at that for a 17 year old vehicle.
Anyway next problem with this -> new alternator. (But we weren't sure if the BCM was at fault or not, in the beginning of this thread)

 

[Communicator]

0.5v while cranking?, most cars drop 3 or 4 volts while cranking.

Perhaps you are thinking of overall battery voltage drop? The measurement was for the drop between battery negative, and engine block, in essence a check on the quality of the two earthing connections.