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Step 1
Inspect the harness wires that hang between the trailer and the hitch. These cables that connect the electrical system of the trailer with that of your automobile, allowing the trailer to respond to braking and turning signals. It should hang with enough slack to not pull out during driving but not so much slack that it drags on the road.
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Step 2
Make sure the adapter plug fits. This is a round plug with a series of circular prongs. If your truck and trailer don't match, adapters are available to fit them together properly.
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Step 3
Take a close look at the cable covers. The hard plastic shell that hangs close to the road should be intact. Often, due to the wear and tear of driving and hauling, these become cracked or have holes that leave the cables vulnerable.
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Step 4
Walk along the trailer and look for exposed wiring leading from the harness. Wires should not be frayed, and insulation should not be destroyed. These problems can affect your trailer's ability to brake and signal properly.
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Step 5
Judge whether the adapter cable should be replaced. This item tends to be abused more than others and must be replaced more often. Be sure the prongs look normal. Check the connector cable too.
