What is the best way to make sure your surge brakes are working? I have a 21ft tandem axle trailor w/disk brakes. Thanks for your help...

At the front of your hitch on the under side there will be a small hole. You can take a screw driver and insert in the hole you should be able to fill the surge brake plunger. You will have to jack your trailer up to get wheels off of ground, if you can get both sides off the ground this way you can check all wheels at once. Have someone spin the wheels, as they are tuning use the screw driver to mannually push on the plunger once the plunger is pushed wheels should stop as in brakes applied. If none of the wheels stop or show any kind of restiantces while plunger is pushed then you got problems. I would start by checking my brake fulid, the cap is located on the top of trailer toung, there should be a silver locking cap take it off and you'll see a black plug remove it and that's where you're DOT 3 brake fluid goes. You can bleed the air out by pushing in on the plunger several times till you see no air bubbles in the fluid. If the fuild reservior is full then you may need to check your pads. The brakes are activated by the silver part of the toung moving in which presses on plunger as your truck stops. Pm me if you need more help.

Great information crankbait1!! Do I need to take the boat off the trailer and then jack up the the trailer? Thanks again crankbait for your help!!!

you can leave it on the trailer, you can also find a steep incline and back up only thing you have to unpulg the lights if you have the kick out seliniod ,the coupler should compress with pressure backing up an incline and you should be able to feel the brakes working against your truck