I want to confirm good grounds on my vehicle. Is there a good way to use a multimeter to confirm different points on the car are making good ground? Are there other methods? Thanks in advance
Meter should read the same as what the 2 leads touching do when testing the meter or very close to it. There are Micro-Ohmeters but way-way over the top for what you are doing.
Yes there is, it's called a voltage drop test. You have to conduct this test with current flowing or it doesn't work. For instance take the starter circuit. With the starter cranking, connect a voltmeter (VOM) with the red lead on the starter case and the black lead to the ground post on the battery. The VOM should not read more than 0.3 volts. If it does, the starter case does not have a good ground to the battery. I used 0.3 volts for a starter because it draws a lot of current. Other circuits in the car shouldn't have more than 0.1 volts on the ground side. So if your headlamps appear to be dim or don't come on, you can test from the ground terminal on a headlamp to the negative battery post. With the headlights turned on, you shouldn't read more than 0.1 volts. Let's say you had a reading of 1.8 volts. Most of the time the ground wire from the headlights goes to a ground somewhere on the front clip. Without disturbing any wiring I would move the positive lead on the VOM to the ground connection on the front clip. If your reading drops to 0.1 volt or less, that tells you that connection is bad and needs to be repaired. The trick for this test is that the circuit you are testing needs to be live with current flowing. I recommend using a long jumper wire with your VOM and leaving it connected to the battery ground post. That leave you free to put the other lead wherever you want and not having to make two connections all the time. There is a very good video that shows finding a bad ground using voltage drop from South Main Auto . While the vehicle he is testing is off topic, the test is very good. His troubleshooting leads him to doing a voltage drop test on the ground at about 39.25 in the video. He confirms that one frame rail has lost its ground due to a very corroded ground strap. You can use the same test to check connections on the hot side of the circuit. You just leave one lead connected to the "hot" post on the battery and check to see that you have within 0.5 volt of battery voltage at your test connection. Again the circuit has to be live with current flowing.
While a simple ohmmeter test will show any gross problems, the voltage drop method is the best way to test, both for grounds and to ensure full voltage to the end device. One place we go 'wrong' is detailing everything with paint (or worse yet, powdercoat) and effectively 'insulating' metal-to-metal connections that establish your grounding. The OEMs were skimpy with paint for a good reason....
Voltage drop testing a circuit while under load is indeed the most simple & effective way to find bad connections.
Here’s a good summary. You know, I’ve never tested a whole car Good thing to do. https://toolsweek.com/how-to-test-a-car-ground-wire-with-a-multimeter/
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