I have a 2019, c63s coupe that has an issue with my radar detector browning out at high speeds. This issue has persisted when using an Escort Redline, a Uniden R7, multiple different cables for each, and when power was sourced from the passenger footwell DC port and now a hardwire to the passenger side fuse box. I recently had a shop hardwire to a fuse on the passenger side and thought that would fix the issue, but it hasn't. When at speeds over about 140 or 150 and if the road is bumpy enough, the detectors seem to just turn off for a few seconds and then come back on. This will happen repeatedly. It is very intermittent, on some roads I can do those speeds and it doesn't happen. I'm not sure if it's the high speeds, the bumps in the road, or the draw from the engine or something causing this. Has anyone run into any similar electrical issues? The dealerships have never been helpful obviously because they can't reproduce this. At lower speeds, these devices work just fine and never have any disconnection issues. It's only at high speeds. Would something like this help?

 

Bad ground or bad connection somewhere is my guess.

 

Yeah I'm not sure. I'm now thinking it has much more to do with the power draw at those speeds and that potentially ancillary circuits/fuses or electronics are shut off over a certain speed. Might try piggybacking a fuse of some system that I know stays on like the infotainment or something.