This is quite bizarre, but I hope somebody can give me some inspiration...

 

When something is plugged into my 12v socket by the cup holders (phone charger, for instance), it screws up the DAB reception, causing it to drop out. The moment I unplug it, signal is restored. I've also noticed that when plugged in and the signal drops, sometimes I can move / wiggle / press the 12v connection and it'll 'fix' it. Really weird.

 

My headunit is the Kenwood DNX521DAB and I've removed it, traced the DAB aerial cable and it's not running anywhere near the 12v socket - it runs straight behind the glove box and up to the windscreen-mount DAB aerial.

 

What on earth could cause this?

 

Thank you if you have any ideas at all!

It could be two things. A slightly 'bad' connection between the plug and socket or bad connections within the plug's transformer.

What happens in a different socket?

Unless I'm missing something spectacularly stupid, I only have the one 12v socket. I don't have one in the boot or in the rear of the car at all, just the one by the cup holders.

Oops.

It's been a year since I got rid of my last VRS so was thinking that there was more than one charging socket in the car....

Okay, back to your problem.

Does it happen with a different charger?

How good is your DAB signal as it can be prone to problems? Is there a way to check this on the Kenwood?

Prob a cheaper charger that's not been emc cert'd causing interference.

The DAB signal is superb usually, absolutely rock solid almost everywhere. I've tried different chargers, including cheapo eBay specials and expensive BlackBerry premium ones, so I'm stumped.

But have you actually checked its strength as DAB doesn't work in the same way as FM. It may be that your superb signal is only just over the threshold?

Sorry, yes, the Kenwood had a display strength indicator and you can see it sit at the highest level, then drop the moment you plug something in. It'll then shoot straight back up when unplugged.

I used to get this problem when I had an VW RCD 310 DAB in my Fabia with a glass mounted aerial. I put it down to a cheap phone charger/cable that was giving off radiation and the skinny cable to the glass mounted aerial that probably didn't have any screening picking up the interference. 

 

Using an external roof mounted aerial with high quality RG316 cable provides a better result.

Inadequate earth?

I used to get this problem when I had an VW RCD 310 DAB in my Fabia with a glass mounted aerial. I put it down to a cheap phone charger/cable that was giving off radiation and the skinny cable to the glass mounted aerial that probably didn't have any screening picking up the interference.

Using an external roof mounted aerial with high quality RG316 cable provides a better result.

That is on the shopping list to be honest, maybe I need to accelerate the idea. I'm plenty happy with the performance of the windscreen mount, but fear a stone chip and replacement windscreen would mean having to replace the aerial.

Inadequate earth?

That was the sort of thing I was wondering, do you know where it is earthed?

Does it make a difference what you plug in? If you plug in the cigar lighter (if it came with one) do you still get the problem?

It didn't come with one so I might need to pinch one from the Mrs Golf to test, but it only starts causing a problem when power is drawn from it. Simply having something plugged in doesn't cause a problem, it's only when it is powering or charging something.

It didn't come with one so I might need to pinch one from the Mrs Golf to test, but it only starts causing a problem when power is drawn from it. Simply having something plugged in doesn't cause a problem, it's only when it is powering or charging something.

It's worth trying. Push it in so it heats up. There's no switch mode power supply or other electronics in the lighter so it will tell you if it's interference or power draw related.

Thank you, I'll do exactly that tomorrow!

That was the sort of thing I was wondering, do you know where it is earthed?

It's probably via the quadlock but you can add another from the rear of the radio to a nearby chassis stud.

Thanks, I might strip it out tomorrow and see what I find. Won't be hard to run a new cable I'm sure.

There is an earth point just forward of the gear lever that the head unit earth should be connect to. You need to take a thick wire from this point to the big earth connection on the back of the head unit.

If the earth for the 12V socket is bad you can get interference on the lighting loom which includes the wires to the glovebox.

Superb, the closer the better! Thank you very much.

Superb, the closer the better! Thank you very much.

Just to clarify...

The earth to the head unit should go to the earth point forward of the gear lever.

The earth from the 12V socket must not.

Thanks for clarifying, I thought you meant to use that point.