BudS

I have a 2012 F150 with the tow package. I have installed the relay and 20A fuse (although the schematic shows a 30A fuse) in order to get 12 V on the 7 pin trailer connector. With the engine running, I measure 14 V at the connector - the same as at the battery. The data sheet that came with the relay and fuse says that line will supply 11.5 A (which seems low to me). My trailer has a small refrigerator that draws roughly 11 A from the 12 V line. When the fridge is on, the voltage at the battery is still about 14 V, but the voltage at the 7 pin connector is a bit lower than 13 V, which is not enough to keep the trailer batteries charged and run the fridge. The 1 V drop from the battery to the connector seems excessive to me. I have towed this trailer with 2 other (non-Ford) vehicles with no charging problems. Does anyone have any thoughts on what the problem might be or how to fix it? Thanks for the help.

isthatahemi

The worst part, is that the voltage sags way lower while travelling, and you will not even be getting 13v when going down the road. I agree this is and issue, and I have no idea what the solution is. Newer vehicles with their high tech charge management seem to exibit trailer power issues. Another example is that once towing, 14 volts is rarely seen, and only when coasting, and only with the cruise control off. You can monitor it through the engineering test mode.