Originally Posted by azflycaster
I would verify the polarity of the city power and/or the city power cable on your TT. If this is reveresed it could cause your water pump to run backwards. It can also cause damage to other devices.
This is a joke, right?
Yes, there is such a thing as polarity to AC power, but it has to do with which wire is attached to the hot side and which wire is attached to ground at the power panel. It has nothing to do with polarity as used in discussions of DC power.
There is no way to hook up AC power to your trailer that can cause your DC power to reverse its polarity. Even if the AC receptacle has incorrect polarity, the DC converter will still produce proper DC.
I also don't understand how this could possibly happen. Your pump is getting DC one way or the other, either from the batteries or from the converter and batteries. The only difference is that when you are plugged into shore power, your DC voltage is probably a bit higher. I don't see how that could cause your problem. Sorry.