Alternator / Stator / charging system failure symptoms.

There are a few very common symptoms related to all charging systems. A lead acid battery is a storage device and needs to be fully charged to test a charging system properly. See the link Batteries page on this site for a more detailed description of the volt DC reading you should be looking for before testing your charging system.




1) I was operating the equipment and the engine shut off and will not re start, I just get a clicking noise and it was running fine just before it quit with no abnormal noises.


2) My battery goes dead when the equipment sets for a few hours.


3) As I was operating the equipment I smelled an odor like acid smell (not coolant-fuel-oil-rubber) and when I look at the battery top it is wet and there is corrosion.


A charging system failure will cause equipment to stop while it is running or not start after it has been setting. A new battery or a fully charged battery and it starts again is a good sign that;


a- alternator belt broken or slipping,

b- alternator not producing DC current


NOTE that the only easy and for sure method to accurately test alternator charge is to use a digital volt ohm meter or simple digital volt meter. If not available (meter) the equipment lights brightness can be observed. After the battery has been charged and installed into the equipment turn the lights on and look at them closely and view the brightness. As the engine is cranked over and the lights go dimmer when the engine starts the lights should go brighter if the alternator is charging DC current.



The proper way is to use the digital volt meter, you can purchase for 10 to 20 bucks like the one in the above link to You Tube. On the DC volt scale (straight line and dashed line on meter Vdc) measure the voltage in the charged battery (minimum 12.6 Vdc maximum 12.8 Vdc) at the lead posts of the battery.


Start the engine and the voltage will go higher and possibly to 14Vdc (volts direct current) if the alternator is charging properly. If there is no change or the voltage begins to drop on the meter after the engine is running the alternator is not charging the battery.



A charging component common is an alternator (AC) that requires a rectifier and regulator, a generator (DC) requires only a regulator.

When a mobile piece of equipment does not crank over it is obviously the battery supply voltage, the cable connections at the battery posts, the ground wires corroded, the starter solenoid not connecting voltage to the starter motor, or the starter motor is not working.

Use a digital volt ohm meter to test voltage in your battery, less than 11.8 volts most likely will not turn your starter. Start the engine and watch the battery voltage on the volt meter, if the voltage goes up to 13 to 14 volts DC your generator system is working and the cause is most likely the battery. If it is higher 14 to 20 volts DC then the regulator needs replaced.

If the equipment starts and charges voltage as it runs and does not re-start because the battery is dropping voltage when setting disconnect the alternator  and see if the voltage still keeps dropping on the volt meter. The alternator is hooked directly to the battery and if the diodes in the rectifier portion of the charging system using the alternator goes bad the battery will be drained when the key is off and will be very low volt reading before starting.

Jump starting another vehicle that has a completely dead battery and you do not allow at least 5 minutes to charge from your vehicle before trying to start the other jumped piece of equipment will damage your alternator regulator circuit. You may not experience a failed charging system for several weeks but for sure you will damage your alternator.

If there is debris and oxidation on top of the battery it is an indication of either over charging from a damaged alternator or one cell is bad causing the charger in your system to keep charging no matter how high the voltage goes in the battery. A bad cell in a battery will destroy the starting and charging systems of mobile equipment. 

You Tube video testing your alternator.