Anytime you find the motors going the wrong direction almost always means the battery got installed in reverse.
Look on the 12VDC battery case and find the word NEG or symbol"-" and make sure this terminal is going to FRAME GROUND. It should be a large WHITE WIRE but someone may have changed the colors.
The 7-way cables should have been replaced wire color for wire color.
ETRAILER.com has utube video on installing the 7-way cable with plug.
If the battery was installed in reverse you will have to look for additional fuses that are blown and will need to be replaced.
Roy Ken
