Hi, I have an 83 watercooled Westy with the auxilliary battery compartment under the driver's seat. I am wondering how to hook up an auxilliary battery. 

   There is a small silver box about 1 inch long inside the battery compartment, this box has 5 wires leading off of it.  Four of the wires have numbers imprinted in the metal next to their connection points. These numbers are 30, 85, 86, and 87,  the fifth wire connection point doesn't have any number. I think this small silver box is called an isolation relay? 

    Someone told me these relays were connected backwards in the vans for 1980 thru 1985, I don't even understand what that means but I'm pretty sure the terminal I want to connect to my positive battery terminal is either the one labelled 30 or the one labelled 87. Ultimately I just want to be able to charge my auxilliary battery when I have my engine running without being able to accidentally drain my primary battery.

Any information  greatly appreciated,Thanks