Mk3 Golf Stereo wiring and multimeter

[twogolfs]

OK, it applies more to higher Voltages more than lower ones but can be considered best practice.

When you attach the black lead first to the earth point then earth is effectively felt at the tip of the red lead, so if you touch it by accident you are touching earth or very close to earth i.e low volts.  If you connect red first, in this case to a high voltage source (I used to deal with up to 1500V DC) you get the same, that voltage is effectively at the end of the black probe.  All it needs is for you to complete the circuit and accidently touch the black probe and through your body you; complete the circuit, you give the volts a lovely big resistor to be dropped across and short a big wadge of current via your body (heart!!) to earth and you wake up with a crowd round you.  If you wake up that is 

I'd use a bulb as well if no MM available. 

[Heyho]

Being that a voltmeter in principle is itself an extremely high resistance, it's debatable as to weather or not there would be enough current flowing to pose a risk of electrocution, but if I were testing 1500v dc, I probably wouldn't want to find out.  Measuring current at those sorts of voltages would certainly require some care, else you'd probably look something like this .> 

Unless looking for a specific voltage, I always choose a bulb or testlight when checking 12v feeds, as applying a small load (even 5w) gives a more reliable result.  I've been left scratching my head before when a DMM has told me that I have a solid 12v, only for it to disappear when it is loaded.