A common thread found in most electrical troubleshooting and diagnostic articles is a stress on the need for good ground connections and the impact poor ground connections can have on circuit/component performance. Based on the frequency with which this issue is addressed, it is reasonable to assume that ground side circuit performance is a concept that resides in the gray area for many technicians. So, we thought this month’s article was a great time to bring together several resources that address this very topic.
An Introduction to Ground Circuits
In this comprehensive series of articles from SearchAutoParts.com, Vince Fischelli addresses ground side circuitry. Ultimately, it appears that this series will include a total of nine articles, though only three have been posted so far. Of what has been published, Vince starts with a basic introduction of how the ground side of the circuit functions and introduces the concept of electron flow, noting that, in a circuit, electrons flow from the negative voltage source (battery negative) to the positive voltage source (battery positive). Visualizing electron flow really helps to reinforce the critical role the ground side of the circuit plays in a properly functioning circuit. Below are links to each of the three installments currently available in the series:
This educational article, from Tom Tillman in Motor magazine, starts with a question: “Which electrical connection is prone to have more problems, the positive (supply) or the negative (ground) connection?” He quickly provides an answer (ground connections have always been more likely to create problems) and goes on to detail the types of issues that can arise and the difficulties in pinpoint a ground-based issue. He provides several useful tips to help you up your diagnostic game, ending with the reminder that the techniques learned to assess and diagnose ground side issues can also be used with positive side issues. “I should mention that wiring connections on the positive side of a circuit are also exposed to the environment and can have problems as well. The systematic approach used on ground testing also works on positive wire connections.” Another great read.
Measuring Voltage on the Ground Side
This video from Pete Meier, also from SearchAutoParts.com, is a great complement to the series of articles from Vince Fischelli above. Where Vince’s articles are focused on electron flow, specifically on the ground side of the circuit, Pete hones in on how to use voltage drop testing to identify that an issue exists on the ground side of a circuit and pinpoint the source of that issue. Quick and to the point, Pete provides an example circuit and shows where and how to take voltage readings to identify the cause of a problem. It is a good investment of five minutes of your time if you are looking to improve your mastery of ground side concepts and voltage drop testing.
BMW Ground Error
Our last resource for this topic, from AutoServiceProfessional.com, provides a great example of the many issues that can be caused by a problem on the ground side of a circuit. Here is a laundry list of problems that can manifest itself due to a ground issue on a BMW 328i, in this case a loose ground point Z6000*4B on the engine block.
- Engine will not start.
- Engine stops running.
- The A/C compressor will not turn on.
- The reverse lights do not work.
- The transmission will not shift into gear.
- Various chassis and engine check control messages are present.
In the trade journals and on iATN.net, we see countless references to vehicle performance issues where the root cause is found somewhere in the ground side of a critical circuit. The above referenced resources are just a tiny fraction of what is out there on this topic. The experts seem to have a consensus that one of the first places to start in your diagnostic routine to resolve an electric system issue is to be sure you have good ground on the affected circuit and any other circuits that impact its performance. Using the concepts and techniques addressed in the above resources can help you resolve ground side issues quickly and effectively.