How to test your grounds

[GNRick]

In the "Ask Ray" column in May 2014 Hemmings Muscle Machines (pages 90-91) someone had a ground problem on their 1972 El Camino. Ray explained that to test your ground wire, set your multimeter to DC volts scale, put the black wire (with an extension wire) on the negative battery terminal and the red wire on the ground wire circuit that you are testing. Then turn on the circuit (such as head light if that is what you want to test). A good ground circuit should have less than .2 volts. If the voltage is higher, then it is a poor ground and you need to find out why. Has anybody tried this? Results? Comments?

 

[gunslinger]

It's called a voltage drop test.
I test automotive electrical systems every day, and have been testing them this way for 10yrs. It's the only way to go.
You can test the condition of almost any circuit in the vehicle, not just grounds.
When doing a continuity test, all you need for the test to pass it one good strand of wire. By doing a voltage drop test, you're actually putting a load on the circuit, and testing it's ability to flow. Any dirty connections, or corrosion in the wire will show up. I try to shoot for .1V or less.

 

[Jerryl]

Hi Rick. Here is a good writeup on this.

http://www.vortexbuicks-etc.com/measuring_voltage_drop_across_a.html

 

[gnpoweredrail]

deal with voltage drop tests everyday all day.
todays vehicles start having issues when the voltage drop is over 3-400 mv on some circuits.
good clean connections and good wire and you wont have issues.
.1 volt or less for sure but I would like to see under 300mv