[kevinm90]

can anyone tell me what the third lead is for on my Passat have positive negative and a smaller lead???:banghead::banghead:

 

[Steve in Chicago]

Can you post a picture of what you're talking about?

From the factory, there is a small tube that comes off the battery and goes down through a hole in the bottom of that bay. This is for venting the battery gasses out of the bay. Could this be what you are asking about?

 

[scotts13]

Positive, negative, and "undecided". Keeps the system in balance.

 

[soundguybob]

The large positive wire is direct to the alternator and starter, the smaller one is B+ to the rest of the systems in the car. IIRC, it goes directly to the buss bar under the dash.