Driving a car with a bad alternator exposes you to a number of risks, which include damage to the car battery from overcharging or repeatedly undercharging.
Replacing a damaged battery with a new one can set you back several hundred dollars depending on the type of battery.
In this post, I cover:
- the 4 most common risks you are likely to face when you drive with a bad alternator,
- the main ways that the alternators fail,
and what damage a bad alternator causes.
How Can an Alternator Fail?
A car alternator can fail in several ways – it may be catastrophic and sudden, where the alternator has no output or partial and gradual, where the alternator generates a lower than expected voltage, excessive damage, or even continues working intermittently.
or you can have a bearing problem, where the alternator makes an abnormal noise because of the worn-out bearings.
So, the nature of the failure of the alternator has a big say in the risks you face as you drive with the bad alternator.
You may want to read: How to read car alternator vs bad battery test.
Tests to Check if Your Car Alternator Works Well
Your car alternator may be damaged if you observe any of the following:
- Dim car headlights when the engine is idling
- Battery voltage reading when car is idling outside the range 13.7 – 14.7 VDC.
- Battery light coming on while driving
For more information on signs that you may have a bad alternator, check out: Will a Car Start with A bad alternator?
The Risks While Driving with a Bad Alternator
#1. Costs of Replacing Car Battery Damaged from Overcharging
A bad alternator with a damaged regulator can overcharge and damage your car batteries. In fact, if your car’s electrical system is not checked thoroughly, you may go through several battery replacements before you realize that it is the alternator that is damaging them.
#2. Car Unable to Start because Battery failed to Charge
When some alternators fail, they are not able to generate a high enough dc voltage to charge your car battery. This results in a partially charged battery that does not have enough power to start your car.
Some faulty alternators with internal short-circuits can also drain the car battery flat, leaving your car unable to start.
#3. Car Losing Power Suddenly while Driving
Your car may accidentally lose power and stop because of a lack of electric power as you drive – both the faulty alternator and drained car battery are not able to supply enough power for the car’s electrical system.
#4. Unreliable Car Performance
If you have a case of an alternator that intermittently charges your car battery, then you may have a case where cannot rely on the car to swiftly start when you need it to. When the alternator charges the battery, the car starts and fails when the alternator fails to start.
Can You Drive with a Bad Alternator?
While you may be able to start and even drive your car with a bad alternator, it is risky to do so because of the dangers damage to your car’s battery, failure of the car to start, and the possibility of your car stopping suddenly from the lack of sufficient electric power from the alternator and car battery.
Should you drive a car with a bad alternator?
Beware of the risk involved, If your car has a bad alternator – ideally you should arrange to have it replaced right away. You may be tempted to drive it if the battery is fully charged and it is a short distance, provided you avoid switching on high power drain accessories like the heater, AC, drive it during the day to avoid usage of lights. Beware of the risks involved though it is safer to use alternative means of transport than risk getting stuck.
You may also want to read: Will a Car Start with a Bad Alternator?
How Many Miles Can You Drive with A Bad Alternator?
There is no one answer fits all – it depends on the extent of the failure of the alternator, how well charged the battery is and what electrical accessories are switched on in your car.
When the alternator dies with no power output, you can only drive the car for as long as the car battery is able to supply electricity to the electrical system.
If the alternator is simply not able to supply the voltage required to fully charge the battery then you will be able to drive your car for a longer distance and possibly for several days until the alternator or battery die completely.
What Damage Can a Bad Alternator Do?
A bad alternator can damage your battery. The faulty regulator in the alternator can result in the battery being subjected to high voltages than the battery was designed to handle causing permanent damage to the battery.
The other way the alternator can damage the battery is when it only partially charges it and combined with the frequent discharges on a partially charged battery causes early battery failure.
How Far Can You Drive with a Bad Alternator?
There is no straight answer to this one – it depends on the nature of the alternator failure and the circumstances under which you are driving.
You may only be able to drive for a few minutes or hours if your alternator output fails all of a sudden as you drive in the night because then your battery drains quickly with the lights switched on.
If on the other hand, your alternator intermittently charges the battery, you may be able to drive for several days or weeks, so there is no one answer that fits all.
What Happens when An Alternator Dies While Driving?
When an alternator dies while driving, your car can suddenly stop for lack of electric power once the backup power source, the car battery is drained and the car’s alternator is not able to produce any power.
You may be able to drive the car for a short distance after jumping it or better still, call for a tow service.
You should avoid driving with a bad alternator, it exposes you to several risks whose impact varies depending on the nature of the failure of the alternator.
The risks faced range from damaging your car battery, car failing to start, and in the extreme, your car can stop as you drive.