Hia Guys

Has anyone come across this as its doing my head in, and the garage has tried 2 diagnostics and come up with Nothing. 

My 66 Focus Diesel, intermittently, tends to Re-Set the electrics for a split second. Odometer goes to Zero, Radio screen blanc and re set. The whole car goes dead, and then back on again as tho the battery has been disconnected. And it's started blowing one of the fuses, so there is no hazard lights I can put on when it decides to do it whilst driving. It doesn't blow the fuse every time, but there's nothing that seems to cause it. The car was quite happily ticking over for 20 mins, I pressed the Engine Stop, and that caused it, whereas last week, it did it whilst driving without touching the engine stop. 

Car is in again on Wednesday next week for another look, Any advice welcome... Cbeers

There is at least a 90% chance that this is caused by loss of the negative connection between the battery and the chassis earth point.

Carefully check, that the battery negative clamp is pushed fully down on the battery post and that it is tight and can't be moved. Check the negative lead from the battery to the chassis earth point is in good condition and that the connection to the bodywork is clean, tight and free from any corrosion. If everything seems to be in good condition my own next move would be to replace the BMS module on the battery negative terminal.