Noticing and recognizing bad ground connection symptoms is crucial to solving this issue in your car.
Why? The first reason is that the ground connection is vital to the proper functioning of your car’s electric and electronic installation.
Second and perhaps more important reason is that this problem often cloaks itself as another more serious one. This can easily lead to unneeded and expensive repairs.
The task of this article is to help and understand this problem better and perhaps find a solution.
If you’re not in the mood for reading, you have a YouTube video tutorial at the end of the article both about the symptoms and solutions to this problem.
WHAT IS A GROUND CONNECTION?
The ground connection on your car is the connection between the minus terminal of the car battery, the car body, and the engine.
In order to explain why is a ground connection so important one must know how an electrical circuit works.
You see, the electric circuit on a car is a closed-loop. It flows from the plus battery terminal to the minus one. Connected to this loop is everything else regarding the electrics and electronics on your car.
For all of this to function, there must always be a continuous and uninterrupted flow of electricity.
When a bad ground connection appears, it disrupts that flow and starts causing all kinds of problems.
To paint a picture, imagine the electricity like water and the whole electric and electronic installation as a pipeline.
A bad ground connection would represent a clog in that pipeline which would then lead to reduced pressure or partial/complete failure of the whole system.
If you’d like more information on this topic, here’s a link from Wikipedia that explains the whole matter in more detail.
BAD GROUND CONNECTION SYMPTOMS
1. HEAVY CRANKING
This is one of the most serious bad ground connection symptoms. It is very similar to having a weak battery or a bad starter.
When you turn the ignition, the starter will crank but barely.
2. LOW ALTERNATOR VOLTAGE OUTPUT
The second most serious symptom. Instead of the 14.2 to 14.5 volts, the alternator voltage output will be much lower.
This symptom is best recognized if you check the alternator voltage. If you don’t know how to do this, you can learn by reading a separate article on this topic or watch a video tutorial on our YouTube channel.
3. FLICKERING HEADLIGHTS
One of the most visible bad ground connection symptoms. When you turn the headlights on they flicker or pulsate mostly due to the mentioned irregular alternator voltage.
4. ENGINE WILL CRANK BUT WILL NOT START AND MAY MISFIRE
A bad ground connection can affect the whole ignition system in various ways.
With gasoline (petrol engines), the main impact is consequently, on the quality of the spark. It will be weak or nonexistent.
For the same reason, an engine misfire might occur although this is rarer (more on that lower in the article).
If the car has a diesel engine, a bad connection may interfere with the relay and heaters.
5. ELECTRONIC GLITCHES
This is perhaps the trickiest of all bad ground connection symptoms as it often mimics other, sometimes more serious problems
I must mention that this symptom is the main culprit for wild goose chases, lots of spent money on unneeded repairs, and lots of lost nerves.
By electronic glitches I mean things like:
Various dashboard warning lights coming up for no reason (or in clusters)
Rear lamps that light up completely-instead of one signal, all of them come up at the same time (the turn signal, position light, everything)
Various appliances showing bad ground connection symptoms in strange conjunctions: like when you turn the blower on, the power window comes down at the same time; you press the brake, and the headlights turn on, and else. (these are just examples, they may not apply to your car but I hope you get the main idea).
What’s also useful to know is that bad ground connection symptoms have a certain pattern of showing themselves. This is very important for recognizing the problem.
Usually, electric problems manifest themselves within their own circuits. For instance, if you have a problem with the cabin blower the common outcome is a bad electric motor, bad fuse, switch, or else.
But if you turn on the blower and the power window comes down it means there is a malfunction in an intersection between these systems.
So if you see weird, uncommon symptoms that affect multiple circuits and appliances at the same time, definitely first check the ground connections.
CAUSES OF A BAD CONNECTION
These are some of the most common causes:
This can happen due to vibration or perhaps a previous mechanical intervention.
For instance, with the body and engine connections, it may happen if the transmission was taken off in the past, like when replacing the dual mass flywheel.
One more cause of loose connections may be damaged threads, screws, or nuts.
Rust (corrosion) on contacts
Like all contacts, ground connections are prone to rust.
The connection from the battery to the car body is better protected as it is usually located higher in the engine bay. It may also have a protective cap on the nut or screw.
The ground cable and ground strap is much more susceptible to this problem.
Since they are mostly located on the lower side of the engine bay or undercarriage, water, moisture, mud, and dirt can easily cause rust.
Most rust problems come from wire lugs at the end of ground straps or ground cables.
Rust will also affect ground connections on various parts of the car body as well as electrical connectors if there’s moisture or water present.
This is one of the most common ground connection symptoms for sure, especially on older cars.
Damaged cables, ground straps, wiring, or connectors
Tears or cuts in the cable or strap, broken wire lugs, damaged connectors, or else, will all cause bad ground connection symptoms.
CAN A BAD GROUND CONNECTION CAUSE A MISFIRE?
This topic has already been mentioned but to be more precise and add a personal experience:
A bad ground connection may affect the whole system (ignition module, ignition coils, sensors, etc) eventually causing a weak or irregular spark which can eventually lead to a misfire.
I encountered a similar problem years ago with a car that had some serious bodywork done together with a complete paint job. When it was put back together it would barely start and when it did, it had a serious misfire.
The car worked perfectly before the bodywork and paint job.
To cut a long story short, a ground connection inside the passenger cabin was painted over. This was causing the problem. After cleaning the connection and putting a couple of new washers and a new nut, the problem was solved.
CAN A BAD GROUND WIRE DRAIN MY BATTERY?
No, a bad ground wire will not cause this kind of problem.
Repairing or cleaning any of the ground connections will probably not solve this issue.
When noticing any of these bad ground connection symptoms, go and check them out before starting any other repair.
With starter and alternator problems, check the main ground connections first (from the minus terminal to the car body and from the car body to the engine).
If electric or electronic glitches are present, check the peripheral ground connections and connectors (located in the engine bay, passenger cabin, trunk, or else).
Make sure that they’re tight, there’s no rust, and that they aren’t damaged. This goes double for the main ground connections.
Again, checking them may well mean the difference between a simple repair that takes minutes and is almost free and spending a lot of money and time on unneeded repairs.
Written by: Sibin Spasojevic
Former car technician, life-long car and DIY enthusiast, author for Despairrepair.com
BAD GROUND CONNECTION YOUTUBE VIDEO