Please Help- Loss of +12v Supply to Radio Loom

[Bascat]

Hi all.

This is my first post to this amazing forum and I am hoping that other members may be able to guide me.

Over the weekend I installed an aftermarket RCD 330 Plus in my daughter's 2012 Golf Tsi using the factory wiring loom. It installed without a hitch and was working brilliantly. i then proceeded to install a pop up reversing cam and tested it several times before final install. Once all of the cables had been run, I made the final connections (identical to how they had previously been made), but upon connecting the head unit, everything was dead. I ran the multimeter across the constant 12v pins on the connector and found no voltage. After checking all of the fuses, nothing was found to be blown. To my surprise, running the meter across the 30A fuse block for the radio in the fusebox under the hood showed no 12v feed. All of the other fuses are showing a 12v supply except the radio circuit. The camera still pops up when selecting reverse and everything else in the car works normally. I also tried plugging the original head unit back in but that isn't powering up either.

I am electrical engineer and have been playing around with car electrics for years, but this one has me stumped. Could there be a master electrical distribution control or relay that has dropped out and pulled power from the radio circuit or is the fault likely to be more straightforward? I am toying with simply running a constant +12v feed (with 30A inline fuse) straight from the battery to the pair of constant +12V feeds on the radio harness, but would like to avoid this if possible.

Any thoughts that you might have would be greatly appreciated.

Thank you.

[VAG-Abound]

Are fuse 8 in the engine and 28 under the dash both good? And the supply side of them?

[Bascat]

I did check all of the fuses when I had the problem, but I will recheck the two that you mention specifically when I get to the car tomorrow. Thanks for taking the time to respond. I will let you know once i have assessed 8 and 28.

[VAG-Abound]

Where are you getting the idea of a 30A fuse on radio from? Diagram I'm looking at says 15A, 20A or 25A (depending on radio type) under bonnet.

That'll be in position 8 of the left hand or 19 of the right hand pictures here: Please Help CAN BUS - Battery Drain - HELP!! - Page 2. Which one do you have?

Start / Stop also affects wiring - does the car have that?

[Bascat]

It is definitely the left hand version of the fuse box. Unfortunately zooming on the image is a little grainy so it is hard to see which fuse is number 8. No stop-start functionality in the car. I will have the car back at home tomorrow so will be able to dig deeper at that time. Thanks again for your help on this.

[Bascat]

I have just checked out the fuses once again, and you were absolutely correct- Fuse 8 under the bonnet had popped (very hard to spot given the unusual way that it blew. Radio now powers up without a hitch, but I have a new problem in that the camera pops up from under the badge and the radio goes into reverse camera mode but then tells me that "the camera is unavailable at this time". It was working before so I am assuming it is a connection issue somewhere. Probably another post for another forum or I will wave the white flag and drop the car to a local VW electrical specialist to sort out. Thanks again for all of your help.