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What is the right output from alternator. My is charging 15.0.Is that to much or it is ok

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No you should be fine anything between 13.5 and 16 volts is good it works

Posted on Apr 21, 2015

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Should be between 13-14 volts is that reading your dash gauge is putting out if so i would check it with a volt meter dash gauges are unreliable they are never calibrated and are usually there for operator reference

Posted on Apr 21, 2015


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Due to the nature of the battery technology used with vehicles the alternator is mostly incapable of charging the battery. The car alternator is designed to keep a fully charged battery fully charged and to provide all the power for the car equipment.

The alternator charge rate is regulated by a voltage regulator. Because the alternator output is connected to the battery, the alternator and battery voltage will be the same and the voltage regulator monitors that voltage.

The lower the battery voltage the more output the alternator will produce in order to correct the situation but because a lead acid battery has a high internal resistance to accepting a charge the terminal voltage will quickly rise to the alternator regulated voltage and fool the alternator into thinking the battery is fully charged when the output will drop to the order of just a couple of amps.

Switch on the headlights or a similar load that will lower the battery voltage and the alternator will increase it's output again - but only by the amount of current the headlamps or other load is consuming.
It matters not what the alternator rated maximum output is, it is designed to provide only the necessary current and no more.

The only time an alternator should ever need to produce maximum output is when on a dedicated testbed and then only for a short duration to avoid damaging the unit. Testing the current output on a modern vehicle is not recommended except for the regulated voltage testing and a rule-of-thumb output test where all equipment is switched on and the engine speed raised while the battery voltage is monitored.

Most modern alternators use an internal voltage regulator but a few systems use a separate voltage regulator. No alternator rebuild would be complete without a regulator test and probably a new or replacement regulator, which is where the majority of charging system problems are, or the brush gear.
Assuming the wiring is ok, no alternator should suffer any harm if the voltage regulator and auxilliary diodes (if fitted) are in good order though fitting a defective or a discharged battery can cause it to overheat and be damaged.

The alternator usually just about stops producing an output when the battery voltage is in the region of 14.5/14.8 volts.
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to drop off a battery cable is one old and reliable way to check charging system. if belts are tight and wiring is correct it is time to put a meter to alt and verify output voltage is within acceptable ranges.....

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It is possible that the extra demand placed upon the charging system finally blew the alternator.
You need to have the charging system checked,,or check the output yourself with a volt meter (should be around 14-15 volts) test must be done with the car running.
If the voltage reads up to 14 or 15 volts then it would indicated a short in the dash control circuit.

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