HOW TO DIAGNOSE A BAD GROUND CONNECTION? -

how-to-test-bad-ground-connection-on-car

A bad ground connection is one of the most overlooked causes of electrical and electronic problems in a car.

When there is a bad ground connection, it can cause all kinds of freak problems that cannot be pinpointed accurately.

This article will show you how to make a proper diagnosis of this problem and remove any doubt.

The most efficient method is at the end of the article.

Besides this website, you can also watch videos on our YouTube channel, where we have many car-related videos that may help with maintenance, driving, etc.

USE A TESTER LIGHT

First, we’ll start with the simplest but least precise method of diagnosing.

You use a tester light, but this time you put the clip on the positive terminal instead of the negative and touch the ground connections.

If the tester light lights up, you have a ground connection; if it doesn’t, there is a problem.

Know that this is not very accurate. Ground connections will sometimes work without an electrical load and stop working under load.

For instance, everything works when you turn on the ignition, but everything shuts down when you try to crank the engine.

USE A MULTIMETER

Next, you can use a more precise multimeter. For cars, set the multimeter to 12 volts DC current.

First, take the tester probes, connect them to the battery, and remember the voltage reading you get.

Then, take the probe from the negative terminal and touch the ground connections on the body and the engine.

If the voltage value is the same as when you started, the ground connection is OK. If it’s weaker or there isn’t a reading at all, you have a bad ground connection.

CLEAN THE BAD GROUND CONNECTION

If you don’t have any of these tools available, you can simply take off and clean all the ground connections.

Also, check if they are tightened; a loose connection will also cause problems.

Start from the battery terminal, clean the body connection, and finally, the connection from the engine to the body.

The engine and body may be connected with a big copper strap or a cable. Know that the strap or cable may not be there at all. On some cars, the engine may be grounded through the engine mount bolts or otherwise.

There are also multiple connections on the car body worth checking, usually inside the passenger cabin.

This is the most labour-intensive method of diagnosis, but if you see a loose or really dirty ground connection, it’s worth a try.

USE A JUMPER CABLE

Finally, the best and most accurate method: use a jumper cable.

Connect one clamp of the cable to the minus battery terminal and the other to either the engine or the car body.

Then try to see if the problem is gone (like weak cranking, for instance).

The jumper cable in this case serves as a bypass for any weak or loose connection.

You’ll give full ground directly from the battery to the body or engine, and also, this way, you can pinpoint the problem.

For instance, you touch the body connection, and the problem is gone; some of the body connections are the problem.

You touch the engine, everything works; the engine’s ground connection is the problem.

If you don’t have a jumper cable, you can use a thicker piece of wire.

CONCLUSION

We would definitely recommend the jumper cable method mainly because it’s the most reliable and simple.

Also, remember that a bad ground connection can mimic various car problems like a bad battery, a bad starter, low alternator voltage, freak electronic problems, and else.

Before giving lots of money for expensive repairs, try checking the ground connections first; it may be worth it.