What Are The Symptoms Of A Bad Voltage Regulator?

What are the symptoms of a bad voltage regulator

If you’re wondering, what are the symptoms of a bad voltage regulator you need to learn that multiple indications will arise, when you have a faulty regulator in your vehicle. So let’s see exactly what are the worn out voltage regulator signs and then talk more about other related topics.

The most common symptoms of a bad voltage regulator are high voltage output, engine check or battery warning light on, non-functional instrument cluster, dead high beams or pulsating front or interior lights. You can also encounter dead battery or oxidation on the battery’s terminals, but also intermittent voltage dips which affect different electronic components.

What is a car voltage regulator?

The car charging system is made out of several components including: car battery, alternator and voltage regulator.

As the name suggests, the voltage regulator assures a constant voltage to the battery and different electrical components.

The voltage coming out from the alternator may have different spikes and irregularities. With the help of the voltage regulator we can have a stable voltage. This assures that the battery will charge correctly and all the systems will function correctly.

We will describe below what can happen if we have a faulty voltage regulator.

Symptoms of Bad Voltage Regulator

1. Intermittent Voltage Dips

If you have a poor voltage regulator, it can trigger other parts, such as a fuel pump, ignition mechanism, or other parts that need a minimum voltage not to operate correctly.

You can feel a gurgling of the motor, a harsh idle, or literally a shortage of momentum when you need it. This does not sound like a huge problem, but it is significant as it demonstrates that voltage is not being handled correctly.

2. High Voltage Output

A standard automobile battery will be designed in an opened circuit of around 12.5 volts (engine is not operating). When the engine is working, the value will be around 1.5 to 2 volts larger for the majority of cars.

If the maximum output is 15 volts or higher, you are most likely to have a broken voltage regulator. In reality, too large a voltage will trigger harm to the different electrical modules. Most often, the lamps in the headlights or taillights are the first to feel the effect of this issue.

3. When Engine Light or Battery Light Warning are turning on

There can be a variety of reasons, so it’s still an idea to look for any DTC (diagnostic trouble codes) when you encounter the Check Engine light. Then if you have the battery warning ON you can run a fast voltage test by using a multimeter and see which component triggers the problem.

4. Instrument Cluster Does not function

Like most electronic devices, the instrument cluster takes a certain amount of power to show most of the details you need when driving. Bad voltage regulators can literally prevent it from functioning or behaving in a correct manner.

The cluster offers critical information during driving like speed, fuel level, engine RPM and so on. That’s why is a good idea to not start driving if you encounter this issue.

5. High Beams Not operating

The headlights are one of the devices that can be negatively impacted by low or high power. In fact, high-beam bulbs need a substantial amount of power to work. Beams that aren’t going to glow adequately mean that there is already a problem.

6. Pulsating or Flashing Lights

You can normally note this with your lamps, but it may impact your inner lamps and also your audio device. Once more, it refers to a voltage which isn’t being well regulated.

This condition occurs for issues connected to the battery, but it may also indicate that somehow the voltage regulator is to fault.

7. Dead Battery or Oxidation of terminals

That may be due to a variety of other reasons, like failing to turn off the lamps, an alternator malfunction, or perhaps an aging battery that needs to be changed. But it may also be attributed to improperly controlled current owing to a faulty voltage regulator.

Oxidation distributed over the contacts and the top of both the battery may be a warning, among other issues, of a malfunction of the voltage regulator.

Driving With A Bad Voltage Regulator

Usually when you want to drive with a bad voltage regulator it may happen that your battery will get fully drained. This means that you will not be able to start your car and you need to leave it where it stops.

This happens if the voltage regulator is fully worn out.

Another problem that you may encounter is that the battery will get overcharged and it can burn several electrical components within the circuit. You might want to prevent this from happening, as electronic components are fairly expensive.

It also may happen that the issue is still incipient and only lamps flickering or audio system is having troubles functioning, but still not an ideal situation to drive with a bad voltage regulator.

In the end, it all depends on how progressive is the problem and if the voltage regulator survives until you exchange it.

Voltage Regulator Failure Causes

In most cases voltage regulator will fail due to numerous voltage spikes. These variations of the voltage can be caused by several things.

We can include:

  • improper connection of the grounding wires – this may cause arches of power that it increases the current and voltage on the regulator;
  • jump starting the car;
  • disconnect various cables or wires while the engine is still turned on;
  • poor electrical connections;
  • charging the battery from the alternator when it’s completely drained – it should be charged separately when it is fully discharged;
  • voltage regulator not properly selected for the current draw;

Will A Bad Voltage Regulator Keep A Car From Starting

The short answer is that is very unlikely. The voltage regulator is responsible to assure a proper voltage when charging the battery.

The only case when the voltage regulator keeps a car from starting is if it was faulty and the battery was not charged. Because of this issue, when the battery is drained, of course the engine will not start.

The simple way to check this is to connect the battery to a jump starter and turn the ignition. If then it starts, it’s a good idea to check what caused the issue.

Remember that when you have a bad or drained battery, the engine will not crank. You will only hear a click and most of the electrical components will not function.

Can A Bad Voltage Regulator Drain Battery

Yes, a bad voltage regulat can drain battery. Like we discussed above, a battery requires a constant voltage to be charged properly. Thus, when the voltage is lower, for example in our case, the battery will charge less.

What this means? It means that the alternator is still charging the battery, but not at the full capacity.

When this happens, a small capacity of battery power is lost each time you drive. In the end, you will notice some of the symptoms described above and probably your car is not going to start anymore.

It might be difficult to figure it out in the beginning. Remember to observe any unusual behavior regarding the electrical components inside the vehicle.

How To Test A Voltage Regulator

You can follow these steps to check if you have a bad voltage regulator:

  1. Borrow or buy a multimeter.
  2. Open the car’s hood and take of the battery caps (if any).
  3. Set your multimeter on DC voltage setting ( a V letter with a straight line above usually Tip: the V letter with a wave is alternating voltage so it should be near that one).
  4. Measure the voltage of the battery with the engine off – should be around 12 – 12.5 volts.
  5. Make sure the car is parked and turned it on.
  6. Measure the voltage of the battery with the engine on – it should be around 2V higher (14 V).
  7. Get some help to rev the engine.
  8. Measure at 2000 RPM – it should be around 14.5 V.
  9. When the value is really higher than this – 15 to 16V it means that the battery is overcharged, usually because of a bad voltage regulator.
  10. When the value is lower in any of the cases, the battery is almost worn out and may need to be replaced soon.


We’ve put in some rows what are the symptoms of a bad voltage regulator,¬†what can cause this issues to arise and how we can check a faulty voltage regulator.

For such a small component, it’s generally ideal to replace it and get rid of all the problems that may come with it.




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