onallcylinders.com/2012/01/16 How to Diagnose Electrical Ground Issues
One of the best things you can do to help ensure a properly grounded vehicle is to replace or add an engine-to-chassis ground strap; Taylor makes a nice four-gauge, braided stainless steel strap ideal for most vehicles.
If you are adding a number of accessories or ones that draw a large amount of current, you should also replace the battery-to-chassis ground with a larger gauge wire. That’s because the factory ground wire is usually a less-than-adequate 10 or 12 gauge. A ground wire must be as large as the positive, or supply, wire to the battery.
Hopefully you will never have to experience the joy of tracing a bad ground. But if you find yourself in such a situation, these tips will help make the job go smoother—and get your ride back on ground level.