The boss has a TJ?(2002) Auto. Every so often the radio will just switch itself off and come back on a few minutes later. She can live with that but a couple of times a week when she goes to start the car in the morning everything is completely dead, no clicking or anything. A jump start kicks things to life and all is OK for a couple of days. Battery is brand new and has been tested OK. Local Mitsub dealer has had a look but can't get problem to replicate. Anyone got any ideas?

The boss has a TJ?(2002) Auto. Every so often the radio will just switch itself off and come back on a few minutes later. She can live with that but a couple of times a week when she goes to start the car in the morning everything is completely dead, no clicking or anything. A jump start kicks things to life and all is OK for a couple of days. Battery is brand new and has been tested OK. Local Mitsub dealer has had a look but can't get problem to replicate. Anyone got any ideas?
Change the battery. Just because it's brand new and tests OK doesn't mean it is OK. I would start there.

Sorry,wasn't clear. It had the fault and so a new battery was fitted and the problem still exists. The new battery has been tested and is fine.

Check the battery terminals and make sure they are clean

When my battery died a few weeks ago, same thing happened, radio turned off and on a few times then the car died all together.

Also check the main power fuse is ok and terminals are clean