RV Repair: how to connect batteries on 87 southwind rv, volt source, test light

Question
My husband has disconnected the 3 batteries on our 87 Southwind RV and now cannot reconnect the wires.  How are they connected?

Answer
Here is a past answer I dug up.  Hope it helps.  

This is critical to how you wire the batteries. Are you using 12 volts or 6 volts? Most trailers use 12 volts, so I use them for your question. You wire 12 volt battery in parallel. Inside the battery compartment you will have two colors of wires. All the manufactures use what ever colors they feel like, so finding out negative and positive is the trick. Here's one way of doing this. Use a 12 volt test light and clip the end to a ground. Plug the coach shore cord into a 110 volt source. Now touch the test light to each end of the battery wires. One of the wires should illuminate the test light through the converter output power. That will be you positive wire. Wire any extra batteries Pos. to Pos. and Neg. to Neg. If none of your wires illuminates the test light. Then check for breakers that may be tipped.