Hi,
If you are towing on gravel or loose dirt, then the brakes should lock up.
You can also check the amperage of the brakes. You should have about 3 amps per brake magnet.
You can also do a simple test at each magnet, with a compos. Have someone apply the brakes manually, and the needle should swing toward the rim as North. Any brake not turning the compos north should be looked at. You might have a broken wire, or shorted magnet.
One post last weekend was about improving brakes. The owner changed the small #14 wire to #8 or #10 wire, that will carry the 18 amps that his RV needed, thus his brakes started working correctly.
It might also be a weak ground connection from the RV to truck that can cause a slight voltage loss, and then they will not work as well.
Sears sells a clamp on meter that measures DC amperage without cutting the wire. Most clamp on electric meters only measure AC in the clamp on section. However the Sears Clamp on meter has both AC and DC clamp on measurement.
If you click on my name, then "View Posts" you can find the brake one from last week, it should be within the first couple of pages. You can refine search with "Brake" and find it quickly. It has some helpful information.
Good luck!
Fred.
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