Harbor Freight Tools


Four-Way Trailer Light Tester

Test your tow vehicle’s wiring with this LED trailer light tester

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Plug this easy-to-use trailer light tester into the 4-flat connector of your tow vehicle and the LEDs light up to confirm the wiring connections. Test your right, left, tail and brake light wiring all with one handy light tester.

  • Fits four-way flat plugs
  • Male and female brass connectors
  • Tests right, left, tail, and brake light wiring
  • Small size fits easily in glove compartment or pocket

66526, 64871, 57234
Housing material
Product Height
1/2 in.
Product Length
1-13/16 in.
Product Weight
0.03 lb.
Product Width
1-1/4 in.
Shipping Weight
0.07 lb.
CA Residents
Warning - Prop 65 Info
Note: Specifications are approximate and subject to change

We guarantee this product to be free from defects in materials and workmanship 90 days from the date of purchase. Limitations apply.