Hi, its happend a few times lately, but i drive my volvo v50 and then when i turn it off.. everything turns off, like i have disconnected the battery! It wont lock or start, no lights and nothing on dash. After a wait sometimes 5mins sometimes 30mins, it all comes back on. It had a new battery last year, and its all connected fine. It can happen before i drive it or after i drive it. Any ideas?

 

There are several "suspicious" connections near the battery on our Volvos. The good news is it should be dead easy to find the problem.

Wait 'til the car is dead, exhibiting the problem you describe.

Get a voltmeter (or even a test light, which will work the same in this particular situation).
Turn something on that will draw current (headlights would be good, but probably just leaving a door open - to turn on the dome light(s) - will be adequate).
Connect the black lead of the voltmeter to a good ground, and touch the red lead to the battery terminal (not the car's connection to it). You should have 12 volts. If not, touch the red lead to the negative terminal (the one connected to the cable feeding the car, not the battery's terminal). If you read voltage, you have a bad ground connection (most likely that terminal / clamp).
Assuming you do read 12 volts at the battery terminal, move to the "next point", which is the clamp / terminal (the one connected to the rest of the car). If you don't have 12 volts there, you've found the problem. If you do, move "down the chain" following the obvious large (usually red) cable, toward the fusebox. When you move from a point where you DO have 12 volts to a point where you DON'T have 12 volts, you've found the problem (it's between those two points).

 

would this work even though i dont have anything working on the car? Lights/locking/nothing on dash? After it doing it last night, it shows errors thismorning.. 'park assist service required' and 'headlight failure service required' reverse sensors have stopped working, but headlights are still working. The time also had changed, and the Bluetooth had disconnected. Would this be part of the problem or another problem?

 

The test I propose should be done only when the car ISN'T working - otherwise you're just going to get "normal readings" that don't tell you anything.

Just wait for the car to not want to start / turn over, and start looking for where you have - and don't have - power.

All those failures are probably just the result of a loss of power to multiple system. If the headlights still work when the rest of the car stops working, don't turn them on to do the test (just leave the car's door open to "turn on" the interior lights, even if they don't come on).