what are some reasons that my trailer brakes would just stop working? I did a search and didn't really find what i was looking for. When I stop it feels like the trailer hits the truck. The fluid is fine. What are some other simple things I can check? THanks in advance

you need to bleed the system.. sounds like you have air in the lines and it is causing a blockage and not activating the accuator for the surge, causing the "clunk" you are hearing on stops.. pretty common in surge brake applications and any les schwab or tire shop can usually do it for minimal cost, if you don't want to bother with the DIY..

thanks i was just reading the thread about DIY bleeding. That will be my next move. Thank god I only drive 8 miles to the ramp

Can be many things if you are sure that the fluid is full then it could be the piston in master cylinder is warn and fluid is blowing by the seals not allowing it to build pressure. If you have drum brakes the remove the tires and drums and inspect the wheel cylinders for warn seals and leaks in the back where line connects. If you have disc brakes look for leaking piston seals oil will be leaking from just behind rear brake pad also inspect the banjo fitting for leaks. Look at the flex lines these are cotton braided rubber and wear out over time should have a rubber hose at each tire on the braking axle for torsion axles or for leaf sprung axles one from frame to axle then hard line along axle. You also have one in the tongue of the trailer if you have a break-away tongue. Lastly if all else checks out check the hard lines and fittings for leaks. Only 3 ways of getting air in brakes first is low fluid and you said that was ok. Second is a leak some where in the system. Third is if you boil the brake fluid you can create air bubbles in the lines. If you boil your brakes you will have purple rotors or drums that are warped, fluid will be very dark and smell burnt. Not saying you don’t have air in lines just very, very unlikely. Good luck!