OK, so I had some time to look at this again today. I've had all the interior trim out at the back of the car, and on the right side (driver's side) I cannot for the life of me see anything that could be a bumper antenna, no wires at all go through the rear of the car at the bottom, or anywhere near it, no antenna amplifier, no co-ax cable, nothing. So while I still stand to be corrected, it very much looks as if my car doesn't have an antenna in the rear bumper. If you still think it does, can you tell me exactly where to find evidence of it, i.e. where the wires are, where the amplifier is? Cheers!
So while in there I spent some more time investigating the antenna in the window on the left side. I tuned to a weak station and it got weaker when I pulled the antenna connectors off, and weaker still when I pulled the co-ax cable out of the amplifier, so that's all as it should be. However at no point could I replicate the problem of suddenly losing all sound. It's very frustrating that the problem is so intermittent, as we all know it's very difficult to diagnose a problem when the symptom isn't present!
I did find that the torx screw holding the antenna amplifier to the car body was loose, so tightened that up of course.
Only thing to note is that the fault is often there when I first turn on the ignition. Today this happened, once the radio has come on and the display is on, sound should come almost immediately, but today it didn't. I thumped the side of the console with the heel of my hand and it started working. This has all the hallmarks of a dodgy connection somewhere in the central console area, so after I'd finished at the rear of the car I slid the radio back out and had a thorough fiddle around with all the cable connectors and harnesses near the radio, and found absolutely nothing - the radio was playing just fine the whole time. If I'd got anywhere near the fault I'd have expected it to lose sound at least for a moment, but it seemed as solid as a rock.
Still perplexed by this one, we'll see how it goes when I next drive the car around, but I'm not confident that the loose antenna mounting screw will have fixed it - we'll see. I'll update again either way.
Cheers!
