One of the rarer car problems is bad alternator diodes.
The alternator in your car produces alternating AC current, but your car’s electrical system runs on direct DC current.
To make this happen and turn AC current into DC current, the alternator has diodes, which are connected to a part called the rectifier.
Although it’s rare, the diodes can malfunction, and because of this, the alternator will work partially or not work at all.
In this video, we’ll show how to recognize the symptoms of this problem, so stay tuned.
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SYMPTOMS OF BAD ALTERNATOR DIODES
1. THE BATTERY WARNING LIGHT FLICKERS OR LIGHTS UP
The first symptom of bad alternator diodes is that the battery warning light will appear on the dashboard.
On most cars, the warning light will shine fully, while on some cars, it may flicker.
In case of the flickering light, if it appears, it is almost a sure sign that the diodes are the problem instead of, for instance, the regulator, brushes, or else.
For more information about alternator problems, click here.
2. LOWER AND FLUCTUATING ALTERNATOR VOLTAGE
After you’ve noticed these symptoms, you’ll probably want to check the alternator voltage.
With bad alternator diodes, the voltage will either fluctuate all the time or will be constantly lower than normal.
For instance, the voltage will be 13.2 volts all the time instead of the normal 14.5 volts.
3. THE BATTERY RUNS FLAT ALL THE TIME
Due to lower voltage, the battery will not be recharged properly, and this eventually leads to a flat battery.
You will notice this as the car will occasionally have a weak crank, but over time, you will not be able to start the car.
Also, bad alternator diodes may cause a parasitic drain, which will also deplete the battery over time.
4. FLICKERING HEADLIGHTS
The fluctuating voltage will also cause a symptom that you’ll easily notice, and that is flickering headlights.
When you turn on the headlights and rev up the engine, the beams will pulse; when the engine idles, the beam will flicker.
5. ELECTRICAL AND ELECTRONIC GLITCHES IN THE SYSTEM
Finally, bad alternator diodes may cause glitches in the electrical and electronic systems.
The frequent fluctuations in the voltage are the main cause of this.
These glitches may manifest as warning lights coming up on the dashboard for no reason, various systems suddenly going haywire, and so on.
CONCLUSION
The solution for bad alternator diodes is to replace them.
The diodes are usually sold together with the whole rectifier, and to replace them, you have to dismantle the alternator.
This is why most people decide to buy a new alternator and replace it, especially if the new alternator is not that expensive.
Also, try to solve this problem as soon as possible, since it can eventually damage the car battery and the car’s electronics.
Written by: Sibin Spasojevic
Former car technician, life-long car and DIY enthusiast, author for Despairrepair.com
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