2007 Holden Astra • 90,000 miles

Hi, I had a wireless reverse camera fitted by an auto electrician, it only works when car is switched off.
they say its a signal problem. And they cant help me.
I want to know if they fit a relay to it, will that fix the problem?
Also, on my trip computer, sometimes it displays REVERSING LAMP, any way, when it shows that, the camera works.
Can someone please help explain it to me, because the auto electrician is not being very helpful.
I had to look up the relay idea.
January 17, 2013.

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