Radio goes to sleep when lights are on....

[dum]

Hello to all again.

I have just finshed restoring my early 250sl.

As my registration plates are to be delivered next week I had never gone around during the dark.

What I discovered today is that when the lights are turned on the radio goes off...

I had a speaker installed at an audio expert and it could have happened there but it is not certain.

Anyone encountered that? Any easy solutions?

Thanks in advance.