The alternator in your car is responsible for running the electrical systems and recharging the battery after the car has been started. If your alternator is not functioning properly, your car may still start, but it will be running solely on the battery.
 Sometimes, it is possible to jumpstart a car with a faulty alternator if the battery has enough charge to keep it running. However, it is important to replace the alternator as soon as possible.Â
Learn more about whether your car can run with a bad alternator and how to identify if your car’s alternator is faulty in this guide from the service experts at Weir Canyon.
Can You Jumpstart a Car with a Bad Alternator?
You can jumpstart a car with a bad alternator if it is dead and you must drive it to a mechanic. Here’s how:
Get a Jumpstart
Use jumper cables to connect your car’s dead battery to a car with a healthy battery. Ensure both cars are turned off before connecting the cables.
Connect the Cables
Attach one end of the red (positive) jumper cable to the dead battery’s positive terminal. Then, attach the other end of the red cable to the positive terminal of the good battery.
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Attach the Black Cable
 Next, connect one end of the black (negative) jumper cable to the good battery’s negative terminal. Attach the other end of the black cable to a metal surface on your car’s engine block, away from the battery and any moving parts.
Start the Engine
Start the car with a healthy battery and let it run for a few minutes. Then, try to start your car. If it starts, leave it running to allow the battery to charge.
Drive to a Mechanic
Once your car is running, drive it to a mechanic to have the alternator checked and replaced if necessary. Avoid turning off your car until you reach your destination, as it may not start again without another jumpstart.
Connect your jumper cables
- Place one red clamp onto the dead battery’s positive (+) terminal.
- Attach the other red clamp to the positive (+) terminal of the working (good) battery.
- Connect one black clamp to the negative (-) terminal of the working (good) battery.
- Fasten the remaining black clamp to an unpainted metal part, such as a nut, stud, bolt head, or bracket, in the vehicle’s engine bay with the dead battery.
How Do You Know if a Car Alternator is Bad?
5 ways to know if a Car Alternator is Bad:
Check the Battery
Start by checking the battery to ensure it’s not the source of the problem. Test the battery’s voltage with a multimeter. A healthy battery should have a voltage of around 12.6 volts.
If the voltage is significantly lower, the battery might be the issue, not the alternator.
Inspect the Alternator Belt
A loose or worn alternator belt can cause the alternator to function improperly. Check the belt for signs of wear, such as cracks, fraying, or looseness. If the belt appears damaged or loose, it should be replaced.
Check the Alternator OutputÂ
Start the engine and let it idle. A multimeter is used to measure the voltage at the battery terminals. A working alternator should produce a voltage between 13.8 and 14.8 volts. If the voltage is lower, the alternator might be failing.
Test for AC Voltage
Set your multimeter to AC voltage and check for any AC voltage at the battery terminals. A small AC voltage (less than 0.5 volts) is normal, but anything higher could indicate a faulty diode in the alternator.
Inspect for Physical Damage
Inspect the alternator for any signs of physical damage, such as cracks, dents, or leaking fluids. Physical damage can indicate internal problems with the alternator and may require replacement.
Learn more about how I can protect my car from damage.
ConclusionÂ
Jumpstarting a car with a bad alternator is possible, but getting the vehicle to a mechanic for repair is a temporary solution.Â
It’s important to follow the correct steps and safety precautions when jumpstarting a car to avoid damaging the vehicle or injuring yourself.
If your car’s alternator is faulty, it’s best to have it replaced by a professional mechanic to ensure your vehicle’s electrical system functions properly.
