Originally Posted by mlinder1958
Is this an issue with 2007 Toyota Tundras as well? I have the tow package w/ 7 pin. I have always taken my battery off the trailer and left it in my garage to keep it out of the So Cal heat. I also charge it there before reinstalling it onto the trailer. So I'm not sure if the battery is charging while driving or not. I'm an electrical dummy, but would I be correct to say that if I hook up my truck to the trailer and check the trailer battery with a voltmeter, the battery, if charging would read 13+ volts?
On the 7-pin connector of the TV, measure the voltage between pin 4 and 1, like tafische described earlier. If your TV is wired and fused correctly, there will always be 12v there, because it's connected to the TV battery circuit. If you have this, and the TT battery fuse is intact, then the TV will be charging the TT battery.