Alternator question

rayjen2k · 16-04-14, 02:47 PM

Hi guys.
Alternator went in my B4 TDI a few days ago.
I bought a rebuilt one off fleabay that was supposed to match.
Unfortunately when I compared them, the new one is missing a place to connect the "DF" wire whatever that is
They both have the B+ and D+ terminals

Can anyone help or should I return it and get another one :/

msh · 16-04-14, 03:03 PM

I have no idea about the way how terminals are marked, but usually third terminal is rpm signal for tachometer. In case of TDI, tachometer signal should be provided by ECU, so it must be unnecessary, but I cannot rule out that it is used by something common to both TDI and TD - like minicheck. Just try.

rayjen2k · 16-04-14, 03:24 PM

Hi MSH.
Just found a bit on google saying that the DF plug is used to send a signal to the ECU to tell it that it is sending out a healthy charge.

Tempted to chance it as I need the car for work

msh · 16-04-14, 04:07 PM

Ah, right, there was something like that - to be more precise, it sends alternator load signal. AFAIK the only use for this is because additional electric heating - glow plugs in coolant for B series, additional electric radiator in heater for C series - is turned on by ECU. But I might be wrong, as I'm not fan of diesels.

16-04-14, 03:03 PM	#2
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	I have no idea about the way how terminals are marked, but usually third terminal is rpm signal for tachometer. In case of TDI, tachometer signal should be provided by ECU, so it must be unnecessary, but I cannot rule out that it is used by something common to both TDI and TD - like minicheck. Just try.

16-04-14, 03:24 PM	#3
rayjen2k Grown up member Join Date: Apr 2009 Posts: 118	Hi MSH. Just found a bit on google saying that the DF plug is used to send a signal to the ECU to tell it that it is sending out a healthy charge. Tempted to chance it as I need the car for work

16-04-14, 04:07 PM	#4
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Ah, right, there was something like that - to be more precise, it sends alternator load signal. AFAIK the only use for this is because additional electric heating - glow plugs in coolant for B series, additional electric radiator in heater for C series - is turned on by ECU. But I might be wrong, as I'm not fan of diesels.