I have a 2007 Stratos, the trailer has surge brakes and I can tell they aren’t working. I’m thinking the solenoid went bad again because I can unplug the lights and back up the trailer without the brakes activating. How can I tell what parts I need. Is there a number on the trailer I can look at? I have never done much work on trailers other than replacing lights. I have no idea where to start on replacing these parts. Thanks