Adapter/Tester Part # 47345 Shows Lighting Circuits Not Working on 2008 GMC Sierra

Updated 06/08/2011 | Published 06/04/2011

Products Featured in This Question

Adapter 7 Pole to 4 Pole with Tester and Cover

(601)

$12.48

Hook Probe Circuit Tester

(60)

$12.27

Question:

The test lights on the 7 to 4-Way Adapter # 47345 top two lights are blinking and bottom doesnt light up Just plugged into truck When I connect the trailer I have no lights on trailer at all. Any thoughts? GMC Seirra 2008 crew cab 4x4

asked by: John

Expert Reply:

You will need to start by determining if the problem is on the vehicle itself or on the trailer.

I would recommend using a tester like part # PTW2993 on each pin of your 7-way trailer connector. Unplug the adapter and test each pin as its function is activated. Activate the left turn signal and test the pin in the 9:00 position. Activate the right turn and test the pin in the 3:00 position. Turn on the running lights and check the pin at the 10:00 position. Then, plug in the adapter and test each pin to eliminate the adapter as being the problem.

If you get a signal at each pin as its function is activated, then the problem exists on the trailer itself. Closely examine the connector on the trailer. Make sure it is not damaged or corroded. If you can see any white or green corrosion on the pins or sockets, the corrosion may be preventing the signal from getting through the connection. If the connector checks out fine, trace each circuit back from the connector. The white wire should be securely grounded to the trailer tongue or elsewhere on the trailer frame. Make sure this connection is not corroded. The green, white and brown wires should be traced back to the lamps they feed. Closely examine the wires for any breaks, or areas of worn or cracked insulation. Make sure each lamp is securely attached to the trailer frame, and that the connection points are not corroded, as the lamps pick up their ground connection by being attached to the frame.

If you do not get a signal at the pins on the 7-way connector on the vehicle, examine the connector on the vehicle for corrosion or damage. There is a socket on the rear of the 7-way that attaches the connector to the vehicle wiring harness. Check this connection for corrosion.

If the connector and its attachment to the wiring harness checks out fine, then there could be a problem with a fuse that protects your towing circuits. These fuses are typically located in the power distribution box under the hood. Check your owner's manual for the exact location.

expert reply by: Mike L