how to tell if it's a bad battery or bad alternator?
47162
However, a very simple way to check if the alternator is working is to run the car and disconnect the positive terminal of the battery. If the vehicle stops running, then you probably have a bad alternator. You can also examine your interior and dashboard lights.
369074
Another simple test is to check your interior lights. An alternator charges your battery when the car is running. If the interior and dashboard lights come on brightly but slowly start to fade, then it indicates a problem whit the alternator.
915418
If your alternator has a bad diode, your battery can drain. The bad alternator diode can cause the circuit to charge even when the engine is shut off, and you end up in the morning with a car that won't start.
4358
Simply jump-start your car and then remove the jumper cables as quickly as possible. Then wait. If the alternator is failing to charge the system, the car will soon die again and you've pinpointed the problem. However, if the car runs and continues to run, then the likely problem is with the battery.
594666
If you hear a whine or the sound goes fuzzy when you hit the gas, your alternator is probably failing. If the vehicle won't crank or start but the headlights are still working, look to problems with the starter or other parts of the engine.
1398036
Bad diodes are a common cause of alternator failure. The diodes are part of the rectifier assembly that converts the alternator's AC output to DC. The alternator's charging output flows through six diodes in the rectifier assembly before it goes to the battery and electrical system.
105364
['The Check Engine Light is On. ... ', 'The Engine is Slow to Start. ... ', 'The Lights Are Dim or You are Experiencing Electrical Issues. ... ', 'The Battery Connectors Are Corroded. ... ', 'You can smell something rotten. ... ', 'Your battery case is misshapen. ... ', 'Your battery is old.']
513529
["High Gauge Reading. An overcharging alternator will cause the voltmeter on the vehicle's dash to read an overly high voltage that may or may not vary with engine speed. ... ", 'Low Battery Electrolyte. ... ', 'Burnt Bulbs. ... ', 'Battery Heating. ... ', 'Swollen Battery. ... ', 'Seeping Battery.']
460642
['A slow starting engine. Over time, the components inside your battery will wear out and become less effective. ... ', 'Dim lights and electrical issues. ... ', 'The check engine light is on. ... ', 'Corroded connectors. ... ', 'A misshapen battery case. ... ', 'An old battery.']
277733
When an alternator is going bad, the battery drains quickly. If the alternator is going or has gone bad, in most cases the vehicle can be driven for a short distance and for a short period of time, allowing you to make it to a service station or automotive parts store for a replacement alternator.
151380
['Slow Engine Crank. When you attempt to start the vehicle, the cranking of the engine is sluggish and takes longer than normal to start.', 'Check Engine Light. ... ', 'Low Battery Fluid Level. ... ', 'Swelling, Bloating Battery Case. ... ', 'Battery Leak. ... ', 'Old Age.']
653722
20-25 miles, if the alternator is completely dead and not charging it. You may be fine if your alternator is working OK. It should keep the engine running once it has been started. But if your battery is dead because it isn't being charged by the alternator, then 20-25 miles max.
387382
There are certain signs of a bad alternator to look for: While running the car, note the brightness of the interior lights. If the dashboard gradually dims, the alternator is likely at fault. Do you notice your headlights running brighter as you accelerate and dimming as you stop?
338379
['Dimming lighting system: The alternator is responsible for passing off the charge to the car battery. ... ', 'Unusual sound: ... ', 'Visual check: ... ', 'Discharging car battery: ... ', 'Rapid clicks: ... ', 'Non-stop rotation: ... ', 'Gear block:']
539689
['Problems with starting the vehicle. One of the first symptoms of a problem with battery cables is an issue starting the vehicle. ... ', 'Corrosion on battery terminals. Another symptom of a bad or failing cable is the presence of corrosion on the terminals. ... ', 'No power to vehicle.']
58659
["Decreased MPG. Although there are other symptoms which can negatively impact your MPG, it's likely to be an issue with your battery. ... ", 'Internal Combustion Engine Running More Than Usual. ... ', 'State of Charge. ... ', 'Unexplained Drop in Battery Bars. ... ', 'Unusual Engine Noises.']
540381
If your car battery is above 12 volts, go for a drive In general, if the battery is showing between 12 and 12.4 volts, it's safe to recharge it using your vehicle's alternator.