I've got a charging issue, and was going around testing ohms between ground points and my battery and had all kinds of different readings. What is the acceptable range?
While we're at it, anyone have a complete list of ground points before I start trudging through wiring diagrams?
Resistance testing of connections is not the best way to approach the problem. You start the engine, apply a load (lights, A/C, etc,) and measure the voltage drop across the connections and wiring.
Voltage drop testing of connections and grounds.
Use a Digital Volt Meter (DVM) to measure the voltage drop across a connection or wire. Adding length to the test leads may be required, and does not affect the accuracy of the test. Use 18-20 gauge wire for the test leads if you have to lengthen them.
1.) Most grounds use the negative battery post as their starting point.
2.) The voltage will be small if the ground is good: less voltage drop = better connection.
3.) Be sure that the power to the circuit is on, and the circuit is being used in its normal manner. For instance, if it is a light circuit, the lights on that circuit should be powered on.
4.) To measure grounds, place one DVM lead on the battery negative post and the other on the wire or connector that goes to ground.
5.) Read the voltage drop: Light duty circuits (1-5 amps) should show .1-.25 volts. Medium duty circuits (6-25 amps) should show .25-.5 volts. Heavy duty circuits (26 amps up) should show .5-.75 volt drop. A voltage drop lower that spec is always acceptable.
6.) See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help for help troubleshooting voltage drops across connections and components. .
Thanks, but I'm kind of confused. Step 4 seems to need 3 leads. Are you saying put one lead on the - post and the other on the ground of the circuit you are testing?
Thanks, but I'm kind of confused. Step 4 seems to need 3 leads. Are you saying put one lead on the - post and the other on the ground of the circuit you are testing?
Charging issue is fixed, although I never found the specific problem. I took a small grinding wheel to everywhere something was grounded, and added a new ground strap from block to the main firewall ground.
Charging issue is fixed, although I never found the specific problem. I took a small grinding wheel to everywhere something was grounded, and added a new ground strap from block to the main firewall ground.