testing for ground

hey, i know that to test for 12v you hook the black probe of the dmm to a known ground and put the red probe to the wire that you think is 12v and if the meter shows 12 volts you know your in business. I was wondering if any of you guys could give me good instructions on how to use a dmm to test for ground. I need to know what mode the dmm should be set to and the whole works. Even though most of the time I will have the wiring color diagram for say a - parking brake wire but I want to know how to test for it if i dont so Thanx

set the meter for continuity, connect the black lead to a known good ground.  then probe the wire with the red lead.  when you have found the ground, the meter will read 0.00 or very close to that.  some meters have an audible tone as well.

put your red lead to 12v and your black to the wire you think of being a neg. say parking liths, when you turn on the suspected neg perking lights, it will go from 12v to 0

k so say i wanna test for the - clutch wire that has ground when the clutch is pressed. I would put the red probe to 12v and i would test the wire i suspect of being the ground wire with the black probe. if its the ground when i press the clutch the meter would go from 12v to 0v? is this correct.

this is why i suggest you set the meter for continutity.  just testing for voltage wont tell you if you have a ground.  it could just mean that the 12 volt connection was broken when you push in the clutch pedal.   just because something reads 0 volts, does not mean its a ground.

rudydapump wrote: put your red lead to 12v and your black to the wire you think of being a neg. say parking liths, when you turn on the suspected neg perking lights, it will go from 12v to 0

This is just incorrect, don't do it this way. All this will prove is the 12volts isn't there anymore, not that it is now a ground.

Mike M2

Tech Manager

CS Dealer Services

Both methods work ok. The continuity [or Ohms] is the one I prefer, ground the black lead, then probe the suspect wire, depress the clutch and you should read 0.00 ,when the clutch is in the up position it will read OL or something. The other way around it is a logic tester .. red light + Green Light - , not always a true ground, but works simple enuf for testing polarity.Tire Proz Stillwater Mn

High End Restyling and Comlete Repair

thanx for all the responses

also can anyone tell me what is the symbol for continuity on the multimeter.thanx