1. Have the battery tested to verify it is good.

2. Start tracing wiring. Start at the outlet in your garage. Then the extension cord you are using, then the input 120V side of your PD4135, then check individual breakers, then the 12V DC at the fuse section one side, your negative buss on the other. Then each individual 12V circuit. Basically you start at the beginning and work your way in.

Thrifty Bill: I have a question I hope you can answer. I'm still trying to figure out whether my PD4135 is functioning properly before finding out on a trip. As I said in my previous thread, I recently took the first trip since the PD4135 was installed and arrived 2 hours later to find out that the trailer battery was pretty dead and I had no lights in the trailer. Back home I checked the 7 pin connector- vehicle side to find the power wire was very poorly connected. Now I'm finding that when the trailer is connected to shore power in my garage, there's no voltage at the trailer battery wires (when they're off the battery). That's not right- is it? The battery is supposed to be charging on shore power- right?