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Trailer Left Turn/Brake Lights Not Working After Installing Hopkins # HM40975 4- and 7-Pole Socket

Question:

i just wired in the 7 way vehicle connector to my 1999 chevy silverrado and the left turn single and bracke light does not work every thing else does

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Expert Reply:

First, verify that the Silverados own drivers-side light functions are working correctly without the trailer connected.

Next check your fuse panel in the engine compartment. Make sure the fuse for the trailer wiring circuit is good; this is, according to my research, the number 1 fuse and should be 40-amp. Also check the trailer left turn fuse, number 10, which is 10-amp.

If the fuses are good then move on to the Hopkins # HM40975 4- and 7-Pole Socket that you referenced. This part uses a round U.S. Car plug-in connector at its rear (please refer to the linked video for illustration). You can disconnect this round plug from the Hopkins socket and inspect its contacts for any signs of green or white discoloration (that could indicate mild corrosion). Use a spray-on contact cleaner as needed. Also look for any contact pins that may be bent. Correct any bad contacts as necessary. Repeat this inspection and/or cleaning on the trailer-side connector.

If this fails to correct the issue then I suggest you test the vehicle wiring with a circuit tester like # 40376. You can test at both the round vehicle connector and at the wiring leading to it; it is possible the wiring is fine but the connector itself is not. Please refer to the linked photo that shows where to ground the tester and apply the probe to test for the left turn and brake signals. Have a helper engage the turn signal; you should detect an on-and-off blinking signal. With the brake applied you should detect a steady signal.

If you do not detect the correct signals on the trailer connector pins then test the wiring that leads to the connector. If you find signals on the wiring but not the connector you can replace the vehicle wiring with part # PK11998. Please note that this harness may use different wire color/function assignments; you will want to wire it to the vehicle by function, not by color. You can use the tester to confirm the function of each wire before splicing in the new connector.

I have linked an article on trailer wiring that may be helpful to you as you go through these troubleshooting steps.

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