testing for ground
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=89505
Printed Date: May 13, 2025 at 12:08 PM
Topic: testing for ground
Posted By: ihkili18
Subject: testing for ground
Date Posted: January 24, 2007 at 7:48 PM
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
Replies:
Posted By: duct tape
Date Posted: January 24, 2007 at 8:10 PM
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.
Posted By: rudydapimp
Date Posted: January 24, 2007 at 8:11 PM
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
Posted By: ihkili18
Date Posted: January 25, 2007 at 12:21 AM
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.
Posted By: duct tape
Date Posted: January 25, 2007 at 6:34 AM
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.
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Posted By: Mike M2
Date Posted: January 25, 2007 at 7:12 AM
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
Posted By: rudydapimp
Date Posted: January 25, 2007 at 9:52 AM
hes not actually wanting to test it for ground. if you reade the post, he wants to be able to read if a wire is a neg, like a parking brake. which is why i said do it that way. - 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
Posted By: Hymer
Date Posted: January 25, 2007 at 10:03 AM
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.
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Tire Proz Stillwater Mn
High End Restyling and Comlete Repair
Posted By: ihkili18
Date Posted: January 25, 2007 at 12:36 PM
thanx for all the responses
Posted By: ihkili18
Date Posted: January 25, 2007 at 1:03 PM
also can anyone tell me what is the symbol for continuity on the multimeter.thanx
Posted By: duct tape
Date Posted: January 25, 2007 at 1:09 PM
it looks like an arrow or triangle pointing to the right, and next to the arrow is a verticle line. sort of like this ->l- -------------
Posted By: ihkili18
Date Posted: January 25, 2007 at 1:20 PM
k thanks its exactly the way you described it and i found it
Posted By: Mike M2
Date Posted: January 25, 2007 at 4:40 PM
rudydapump wrote:
hes not actually wanting to test it for ground. if you reade the post, he wants to be able to read if a wire is a neg, like a parking brake. which is why i said do it that way. - 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
I think you need to re-read his post! He specifically states he wants to test for ground!!! ------------- Mike M2
Tech Manager
CS Dealer Services
Posted By: rudydapimp
Date Posted: January 25, 2007 at 4:50 PM
but he is asking how to test for a negative wire, such as a - parking wire, if he doesnt have a wiring diagram.
Posted By: duct tape
Date Posted: January 25, 2007 at 6:21 PM
a negative circuit will show ground or very close to it when activated. i think you are losing this argument, time to walk away  the thread title also states that he wants to test for ground -------------
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