Like Jim said, there is a 4" square junction box, but it may be inside. Ours is behind the couch. Also like Jim said, be sure the electric is off. I prefer to disconnect from shore power. One other thing to consider is when bringing the slides in, do not try and relieve the pressure built up in the hydrolic system by pushing the button to extend the slide. Even for an instant. It is that built up pressure that holds them in place. I say this because I don't know what procedure your bro in law uses when retracting the slides.
Please let us know what the final cure was.
Peace
Dave