When you say "tighten brakes" does that mean you have adjusted them? Because the large majority of the time, weak trailer brakes are a sign that they need a proper adjustment, and the hum is an indication that there is some power getting through. I have added a link below to a help article on trailer brake adjustment you may want to check out. However, if you have already adjusted them there are a couple of other issues potentially causing the issue.
The largest possibility is that you... view full answer...
Go To Results