Boat Trailer Lights Do Not Work with 7-Way to 4-Way Adapter with a 2005 Toyota Tundra

Updated 07/12/2012 | Published 07/11/2012

Products Featured in This Question

7-Way RV to 4-Way Flat Trailer Connector Adapter

(126)

$20.91

Hook Probe Circuit Tester

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$13.35

Question:

Used the adaptor on the Tundra. Boat is wired correctly. Nothing works. Possible solutions? Checked fuses on the truck side. Good ground leads.2005 Toyota Tundra 7 point to 4 flat problems

asked by: Jack C

Expert Reply:

There could be a problem with the adapter, or it could be pinned out differently than your truck. First, use a circuit tester like # PTW2993 if needed to test the 7-Way on the truck. If all the functions on the pins are working properly, you can eliminate the truck as the problem.

If they are not working properly then that would indicate a problem on the truck side and you will want to check all the relays/fuses related to the tow package wiring.

If the truck checks out ok, plug in the adapter and test the 4-Way end with the circuit tester. If the functions are not coming through to the 4-Way then either the adapter is bad inside or the 7-Way on the truck and the adapter are not configured the same. The adapter will be configured like in the diagrams in the FAQ I have linked.

If the 4-Way does show the correct signals then that leaves the trailer as the culprit. Most likely you are looking at a bad ground. Make sure the main ground and all of the light grounds are attached to clean and corrosion free bare metal surfaces. If it is an aluminum trailer, sometimes aluminum does not provide the best ground and you will need to attach the light grounds to the main ground at the trailer connector.

expert reply by: Michael H