Another thing to check would be the speaker wires, make sure they're not earthing out on the body as sometimes that can cause all sorts of weird problems (From experience).

I had the same problem on my MG. It might be the alternator which isnt charging the battery properly. I managed to solve my problem by switching to a more powerful bosch battery rather than the cheaper halfords one.

The radio may be pulling excessive current at higher volume.The automobile circuits of today are designed to keep owners from working on them. They have resistive wire,very marginal sized wire and interlinked circuitry which if inbalanced will not work properly.

I too would suspect there's a massive amp fitted to it. The standard radio draws very little juice, at least over a short period.

Hi so is this a standard radio package or as he like most young persons fitted high power amplifiers which would make it almost impossible for the standard battery to deliver enough to do both.

or of course the radio is faulty.

sounds like there,s a short in the radio !

My friend has a weird problem with his car

Its an s reg golf which will start but if he has his radio on past a certain volume ( I think its when the volume is on 24) and he turns his car off it wont start again.

I have tested the battery and it is fine seeing as the battery is near new. I wouldnt have thought it was ignition as it only wont start if he shuts it off with the radio on?

Any suggestions?

Thanks.