Does anybody know where the common earthwire is on a 392334 factory fitted decoder I'm trying to fit some stay alive capacitors to use this locomotive on m-track and I can't find a manual anywhere I don't want to go in and just prod with a multimeter and hope I find something. Common earthwire is often referred to as the programmer ground.
Loco is modern new 3000.
Thanks in advance

Hi Clive
I cannot find the loco you mentionned (392334) but the little I know is:
- all factory-fitted decoders follow the same Märklin's wire colour code
- in this code, the frame ground, coonected to the wheels is BROWN
- the common wire for fonction return is ORANGE. It is the RECTIFIED PLUS 5Never to be connected to the frame ground). Pin 16
- the common wire for the MINUS RECTIFIED is pink. This is Pin 20 in the 21MTC)

Here is the full colour code table for MARKLIN (NOT NEM). See green frame


Since more than a decade, Märklin uses the 21MTC (Märklin, Trix Connector)
The assignment of pins is as follows


I hope this helps

Note: when purchasing a mSD3 decoder with a PCB base, there is a special connector to connect the power module through a SUSI interface for configuration and shut off

Cheers
Jean