The wiring adapter plugs right in to a connector in the spare tire well of the Volvo. The wiring assembly comes with a grommet pre-installed, so that the wire passes out through the bottom of the spare tire well right by the receiver hitch.
The wiring assembly is meant to be used with a Volvo OEM hitch, which presents a vertical, rear-facing surface to mount the 4-pin plug to. The wiring assembly comes with a bracket having a 90 degree bend that is configured for that vertical, rear-facing surface. My "Hidden Hitch" brand receiver hitch didn't have a similar place to mount the bracket, so I unbent the bracket to make it totally flat, then mounted it to the underside of the Hidden Hitch.
I drilled and tapped a 1/4-20 hole into the underside of the hitch so that I could affix the bracket. My cordless drill was a bit too big to fit under the hitch, so I used an air-powered angle drill. I could have figured something else out, e.g., jacking up the rear of the car, but the angle drill worked fine.
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