This might help. They also may just need adjusted and the dealer should do this for you before taking it. A good mechanic should be able to do that in a half hour - worth it even if you have to pay for it. Should be adjusted out until they fully engage then backed off 8 clicks for Dexters.
On electric brake systems, the operation of the brakes can be checked by activating the emergency stop system to see if it brakes the wheels, or by unplugging the trailer from the vehicle and energizing the trailer brake control circuit with a 12-volt battery to apply the brakes (be sure to use circuit breaker or fuse-protected jumper wires). If the brakes fail to apply, check wiring continuity, the trailer circuit breaker or fuse, ground connections and magnets.
Even if the brakes apply normally, the only way to know for sure if they are adjusted properly is to test drive the trailer behind a vehicle.
On electrical systems with adjustable gain, the amount of braking can be adjusted up or down to match road conditions, load and driver preference. Heavier loads require more braking force than light loads. Rough, loose road surfaces or wet roads require less braking force to prevent wheel lock up.
Before the gain adjustment can be properly set, the brakes need to be warmed up by driving a short distance (1/4 mile) at 25 to 45 mph with the brakes lightly applied or by making a series of stops. Warm brakes are more aggressive than cold ones so it is important to make sure the brakes are warm before any gain adjustments are made. Also, the trailer should be loaded normally to simulate real-world driving conditions because the amount of gain that is needed will depend on the load.
Tow the trailer at approximately 25 mph and brake normally on a dry, paved road surface. Gradually increase the gain (brake force) until the brakes just start to lock up, then back off the gain until the trailer comes to a safe, steady stop without the brakes locking up. If the control also has an adjustable delay setting, this too should be fine tuned so the tow vehicle and trailer work in harmony when the brakes are applied.
If the trailer brakes seem to be operating normally in the service bay, but the trailer does not brake properly when it is being driven, the problem may be in the vehicle controller. Some controllers have built-in diagnostic LEDs that illuminate to indicate various operating conditions and faults.
If you suspect a vehicle controller problem, connect a voltmeter or 12 volt
test light to the vehicle's trailer connector and check for maximum voltage output when the controller manual over-ride button is pressed. If you do not see maximum voltage at the trailer connector within three or four seconds, check the voltage output at the controller. If the controller is putting out the specified voltage, the problem is in the wiring between the controller and trailer connector. If you do not get the proper output from the controller, the controller may be bad.
A controller may not work properly if it is not picking up a signal from the brake when the brakes are applied. You should see a voltage output from the controller when the brake pedal is depressed with the key on. If there is no output, check the connection between the brake light switch and controller. Also, make sure the controller is getting voltage from the battery and is properly grounded.
Inertial-style controllers must also be installed in the proper position (level or within a specified number of degrees) to sense changes in momentum properly. If someone has remounted or moved the controller, it may have upset the brake adjustment.
Electrical braking problems may also occur if the wires used to carry the current are too small for the amp load in the trailer circuit. Wires should be 14 gauge or larger for both the positive wire from the controller and negative ground wires back to the tow vehicle. Wiring connections should be soldered or joined with compression (crimped) connectors, not pinch-style connectors. Also, the trailer frame and brake cluster backing plate should not be used for ground connections. Brake magnets in the trailer should also be wired parallel (not in series) for optimum performance.