Testing ground using ohm-meter?
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Testing ground using ohm-meter?
im trying to test the grounds on my truck,
I have a meter,
Do I use volts or ohms?
I tested volts to the chassis ground from battery and got 10-11v,
Does that mean its grounded? or not grounded?
its seems the info I find isnt quite what im lookin for,
Im trying to see if my EEC has power/good ground
I have a meter,
Do I use volts or ohms?
I tested volts to the chassis ground from battery and got 10-11v,
Does that mean its grounded? or not grounded?
its seems the info I find isnt quite what im lookin for,
Im trying to see if my EEC has power/good ground
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From: Moscow, Russia
Ohms with disconnected battery between different parts - i.e. engine/cabin, cabin/frame and so on. If the connection is ok, you get 0 Ohms. EEC is grounded as long as the cabin is grounded, which usually means "always". Why are you testing it?
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From: Dallas area
Our trucks have 12 volt DC (direct current) systems. This electricity comes from the battery and the alternator. Testing the battery from the positive terminal to ground while on the DC volt scale and you obtain a 10-11vdc reading shows your 12v battery is a little low. When you switch the ohmmeter to the ohm scale you are checking the resistance of a circuit. This is best done with the circuit isolated. For example, when on the ohm (resistance) scale, if you touch the red lead to a place on the frame and then the black lead to another place on the frame, theoretically the resistance should be zero. You have rust and paint so you may see more then zero. So if you want to check a circuits resistance to ground, if it is supposed to be grounded you would put one of your test leads on that pinpoint and the other to a known good ground. It should read
close to zero or zero. If not, you have an open circuit or a high resistance to ground, and need to repair that ground circuit. The ohmmeter function is also useful for checking circuits that may be shorted together that aren’t supposed to be or power circuits that are shorted to ground that aren’t supposed to be, referred to as a dead short and often results in burnt wires or blown fuses. You can also use the ohmmeter function to check the resistance of various components, if a coil is supposed to have 20-70 ohms, for example the EVR, you would touch one lead to each terminal of the coil, and you should read that amount of resistance on your meter. If the coil had an open, your meter would show infinite resistance or something in the range of mega ohms. Anything less then 20 ohms would indicate there was a problem with that coil. The meter is useful for power checks as well. When on the Volt DC scale you can look for power at various points to see that power is reaching that point by using the red test lead on the test point and touching the black lead to a known good ground. This would tell you if you have power going to that point.
close to zero or zero. If not, you have an open circuit or a high resistance to ground, and need to repair that ground circuit. The ohmmeter function is also useful for checking circuits that may be shorted together that aren’t supposed to be or power circuits that are shorted to ground that aren’t supposed to be, referred to as a dead short and often results in burnt wires or blown fuses. You can also use the ohmmeter function to check the resistance of various components, if a coil is supposed to have 20-70 ohms, for example the EVR, you would touch one lead to each terminal of the coil, and you should read that amount of resistance on your meter. If the coil had an open, your meter would show infinite resistance or something in the range of mega ohms. Anything less then 20 ohms would indicate there was a problem with that coil. The meter is useful for power checks as well. When on the Volt DC scale you can look for power at various points to see that power is reaching that point by using the red test lead on the test point and touching the black lead to a known good ground. This would tell you if you have power going to that point.
Last edited by 5Rangers; Jun 7, 2011 at 05:54 PM.
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thanks,
that was alot more helpful,
so when checking for ground I need to disconnect the battery? Both cables?
If I was checking the resistant of the frame to motor ground, I would put a lead on that ground and the other lead on the battery ground?
that was alot more helpful,
so when checking for ground I need to disconnect the battery? Both cables?
If I was checking the resistant of the frame to motor ground, I would put a lead on that ground and the other lead on the battery ground?
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From: Dallas area
For doing non power checks such as checking grounds and continuity, disconnecting only the negative cable on the battery is enough to take power off everything. An additional benefit of only disconnecting the negative side is no big sparks when reconnecting.
You should see a very low to no resistance when checking on the ohmmeter scale from the engine block to the frame rail. Painted surfaces and rust will increase resistance. If your engine to frame rail ground is working good you would put your test leads on any other area on the block and the frame other then where they make their connections to verify the ground wire is doing its job. If you didn't see a low resistance then you would want to check that cable and the points where it attaches for corrosion and loose connection and check the cable itself for low resistance aka continuity.
Simply put, the negative cable attaches to the block, the block attaches to the frame, the frame attaches to the body parts this puts the entire truck on the same electrical potential.
On our old trucks bad grounds are often the culprit of numerous problems. A good ground has to exist for any circuit to work as the electrical current has to have a path back to complete the circuit. Think of your battery as a reservoir storing the electricity, the electricity flows out from it through the various components where it gives them the power to do their jobs and then it should make its way back. The altenator keeps the reservoir full and provides power to other electrical circuits as well especially during high demand.
You should see a very low to no resistance when checking on the ohmmeter scale from the engine block to the frame rail. Painted surfaces and rust will increase resistance. If your engine to frame rail ground is working good you would put your test leads on any other area on the block and the frame other then where they make their connections to verify the ground wire is doing its job. If you didn't see a low resistance then you would want to check that cable and the points where it attaches for corrosion and loose connection and check the cable itself for low resistance aka continuity.
Simply put, the negative cable attaches to the block, the block attaches to the frame, the frame attaches to the body parts this puts the entire truck on the same electrical potential.
On our old trucks bad grounds are often the culprit of numerous problems. A good ground has to exist for any circuit to work as the electrical current has to have a path back to complete the circuit. Think of your battery as a reservoir storing the electricity, the electricity flows out from it through the various components where it gives them the power to do their jobs and then it should make its way back. The altenator keeps the reservoir full and provides power to other electrical circuits as well especially during high demand.