Strangest/most amusing electrical 'qwerk' yet!

OK, I've decided my RRC doesn't have problems, it has qwerks instead!

Anyway, this is a new one: I fitted a headunit today (car didn't come with one), and bought an ISO cable so it was a 'plug & play' job rather than having to splice wires and the like.

The headunit constantly displays "MUTING 0" and won't do anything - play CD's or the Radio - whilst it shows this message. Also, this message/error code isn't listed in the manual, which is helpful.

Here's where it gets weird though - switch the lights on (sidelights or headlights) and the radio immediately comes to life! CD works, Radio works, it even remembers stations and everything! Switch the lights off, and sure enough it goes back to MUTING 0.

So, any ideas? I'm reasonably au-fait with stereo wiring, but this one has certainly bemused me! Any experts on here?

Cheers!

i'd hazard a guess at the phone muting wire getting voltage it shouldn't. Find out which wire that is and disconnect it to see if problem goes away

Definitely that. The original radios fitted to these had illumination that was dimmable along with the dash lights. That's what you have connected to your mute circuit.

Awesome, thanks guys - that orange wire is getting the snip in about 5 minutes time!!