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Installing a Trailer Wiring Converter on 1998 Dump Truck  


Have a large implement trailer, 7 spade plug, and all the lights function perfectly with my two year old pickup truck. Recently purchased a 98 dump truck and it had an unusual trailer seven spade receptical that would not fit my trailer plug. Purchased a new receptical socket and swapped it out. Noticed there was wire for hot, and brakes. All the lights function properly except no brake lights on the trailer. How can I make the dump truck socket brakeinch work with the trailer plug a as it is.?


Expert Reply:

You'll need to use a circuit tester like # PTW2992 and test each pin on your 7-way as its function is activated. The pin in the 3:00 position should light up when the right turn signal and when the brake pedal is activated. The pin in the 9:00 position should light up with the left turn signal and brake pedal.

I'm guessing when you test, you're not going to get brake signal at those two pins which means that the signal you're getting is unconverted.

To fix things, you'll need to install a taillight converter like part # C59496. You'll install the converter inline on the wiring feeding the 7-way on your truck. Once again, use your tester on each wire feeding the 7-way, looking for the brake light circuit, the right turn, left turn and the running light circuit. Connect the input wires of the converter on the wiring feeding the trailer connector, cut the 4pole plug off the output side of the converter and connect those to the 7-way according the diagram I've provided and the wiring diagrams I've linked you to.

expert reply by:
Mike L
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Ronald M.


I need a 7 spade trailer plug for my 1991 gmc k7000 dumptruck do you have anything that will work

Etrailer Expert

Chris R.


For a standard 7-blade connector on your K7000 you'd need to go with a universal type setup like the Draw-Tite # 20023, which provides a longer 7 foot lead that will be helpful when wiring up a larger truck like this. Installation will just be a matter of locating all the correct wires to tap into on the truck using a circuit tester.

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