An alternator can fail in various ways; the most common is undercharging and draining the battery. However, a broken alternator can also overcharge and send the voltage throughout the electrical system.
An overcharging alternator can do a lot of damage. Identify the symptoms of an overcharging alternator and what you can do before any other components get damaged.
What Does It Mean When Your Alternator Is “Overcharging”?
“Overcharging” is a term used to describe an alternator producing an output beyond what is rated for.
This understanding is a little important because alternators are preset to output, in terms of voltage, within a given range.
This range is even the operating threshold at which electronics for a certain vehicle operate.
An overcharging alternator can quickly and easily destroy sensitive electrical components and make them useless, incurring hefty costs to repair that far exceed the cost to replace the alternator.
An alternator’s output is regulated by an internal voltage regulator, which prevents overcharge, but a failure of the voltage regulator, like all things, can and does fail intermittently. And excess voltage can build up quickly.
Most voltage regulator components built into alternators limit output at approximately 13.5-14.5 volts, so anything greater than 14.5-15.0 volts could result in a fault for overcharging.
Always check factory-specific service literature for your vehicle to confirm.
Symptoms of an Overcharging Alternator
An overcharging alternator can often be identified by recognizing one or more symptoms associated with such an event.
Knowing those symptoms can often be helpful when trying to catch problems of this nature quickly.
Below are some of the most common symptoms associated with alternator overcharging.
#1. Irregular Dash Readings.
One of the most evident signs of alternator overcharging is the faulty high reading on your vehicle’s instrument panel voltage gauge.
In any case, if your vehicle ever indicates an excess of 15 volts, you may want to begin asking questions. If your reading is many volts above this value, you are likely to have a problem, especially if it’s a warning on your navigation screen.
#2. Battery Abnormalities.
If your vehicle’s case battery suddenly appears swollen, or your under-hood inspection shows the vehicle’s battery is unusually hot, it’s almost certainly an overcharging alternator.
You could also see the boiling of the battery electrolyte or start to detect a sulfur-type smell coming from your vehicle’s battery.
#3. Shortened Bulb Life.
In some cases, an alternator’s charge excess can be seen on the instrument when you replace your vehicle’s headlights, fogs, or marker light bulbs. This is especially true if it seems like you are replacing your vehicle’s bulbs more often than you should.
This symptom by itself comes from greater loads on a particular bulb, due to carrying excess voltage in the circuit.
What causes an alternator to overcharge?
In almost every example, a defective voltage regulator is the cause of the overcharging. As implied in the title, a voltage regulator regulates the total electrical output of the alternator, maintaining the output voltage and preventing any excessive output voltage.
Every alternator is paired with a voltage regulator unique to that manufacturer, and most of the time, the voltage regulator is built right onto the alternator itself.
Most of the time, this regulator does not allow an alternator to provide charge rates above 13.5-14.5 volts, and if this component fails, the alternator has limited voltage control.
While it is much more often that an alternator fails in the manner that it cannot produce voltage, and I acknowledge that like any consumer grade product, voltage regulator failure, and as often with it overcharging, does happen, and this condition is frequently found by the proper use of a decent digital multimeter.
Can a Bad Ground Cause an Alternator to Overcharge?
Yes, A bad ground can cause an alternator to overcharge; a clean, secure ground path is necessary for the alternator to properly regulate the voltage output.
If the ground wire is loose, corroded, or damaged in some way, it will introduce high, unregulated resistance into the circuit, which in turn interferes with the voltage signal traveling between the alternator and the engine computer (ECM).
Every time the ground path is interrupted, the alternator cannot receive the voltage signal accurately based on the load requirements, which will then lead to an overcharge to the electrical system of the entire vehicle.
Where the control unit or ECU knows it is receiving an overvoltage condition but cannot remedy it because of the bad ground connection to the alternator, it cannot receive the proper signals that it is supposed to.
Can You Keep Driving?
In general, it is never advisable to keep driving with an alternator that is overcharging, as you will almost certainly damage the battery in this time as the electrolytes boil over.
Additionally, keeping a vehicle above its intended operating voltage puts undue stress on sensitive circuitry inside various control modules.
In the worst-case scenarios, driving the vehicle for some time in an overcharging condition could require a repair that is more expensive than just replacing the defective alternator.
The longer you let the vehicle overcharge, the more likely that damage will happen.
In either case, the overcharging condition on any given vehicle should be diagnosed at first availability and repaired to avoid those headaches, and it might reduce more costly repairs for secondary repairs.
If you are not comfortable performing such repairs, make an appointment at your service center of choice at your earliest convenience.
How to Fix An Overcharging Alternator
In almost every case, the only solution to alternator overcharging is to replace the defective alternator.
This solves all concerns of this nature and completely isolates the problem of the overcharging complaint because the alternator’s voltage regulator is only built into the alternator assembly.
While it may be able to be rebuilt and have the voltage regulator changed, it tends to be more work than it is worth to change an alternator in its entirety.
The practice of rebuilding alternators, at least for the most part, barring special circumstances, has nearly disappeared anyhow.