Function Common Positive on a 44913 DCC Decoder??

[ftherrmann]

I've pulled the engine apart and am ready to install the decoder.  Everything on the wire harness makes sense except the (Blue) "Function positive common" wire. 

I'm new to DCC and N scale but I'm guessing that this needs to be wired to the one of the engine halves?

My understanding is that when using the Bachmann EZ command controller a constant 16v AC is applied to the tracks and the decoder rectifies and regulates voltage to the engine motor.   Could someone explain to me what function the blue wire serves?  It seems redundant since since the left and right rail pickup already provide this connection. 

Does it matter which half of the engine I connect the blue wire to?

Thanks in advance!

Fred

[richg]

The blue function wire is common for lights . Connect it to the chassis and bye bye decoder.
Take time to learn how decoders are wired before doing anything with them. You will save your self money and eliminate grief. Decoders come with instructions for wiring into a loco.
The blue wire is positive common for light functions.
All light wires are negative voltages.
Guessing with DCC will get you into trouble every time.

Rich

[ftherrmann]

Rich,

Thanks for the info..  Needless to say the reason I was asking was because I didn't know what the function of the "common positive" was and it wasn't explained well in the Bachmann instructions.  Normally a common is usually just referred to as the "common".  But in retrospect the white wire is referred to as the "Function Output A" and the yellow as "Function Output B".  Guess I could have associated "function output" with "function common".  But like you said why guess and smoke it...

I also found a good write up about DCC wiring at the following url:  http://modeltrains.about.com/od/electronicsdcc/ht/Install-A-Dcc-Decoder.htm

I just finished wiring it (Northern 4-8-4 N scale) up and am going to ring it out with the ohm meter tomorrow before I unpack and read up on the E-Z Command Control system. 

Thanks again for the input!

Fred

[richg]

You probably know by now but all decoder companies have the decoder manuals/documents on line. Some never take time to properly check for documents. Never, ever guess with DCC. It will bite you. With all the forums I belong, to, I see it quite a lot.
Good luck.
I have been in electronics for over 50 years and most of the time, common was the negative voltage in devices.

Rich