Using a multimeter you set the range to match the expected reading - you do not say what you are trying to check - continuity/resistance (Ohms) or Voltage.
Do not try to measure Ohms on an active (live) circuit - the meter may not like it.
Ohms readings are best done with the component under test out of circuit i.e. one terminal disconnected - the reading may not be accurate otherwise.
Any old multimeter will do - they are all much of a muchness - I am unable to help you with diagnosis - sorry.
Good luck...
Peccavi
May 2010