You may need a new one. It might not be capable of charging as well as it used too.
The voltage regulator in the alternator is probley weak. Replace the alternator
Any alternator will charge at idle.
Alternator belt is slipping. Tighten or replace as necessary.
between 13.5 and 14.5 volts with engine running at idle
Yes and no. Yes: The alternator will charge the battery any time the engine is running (even at idle) if the battery's voltage is below the threshold (usually around 12 volts) so that the voltage regulator triggers the alternator to generate power (around 14 volts) until the battery is charged up. No: If there is not enough consumption of power, the battery may be charged enough and the voltage regulator will not trigger power generation.
Engine idle is too low, alternator drive belt is slipping, alternater is defective, voltage regulator is defective.
Because your alternator starts to generate more power as you accelerate, as opposed to an engine at low speed or idle. The car reads this extra voltage from the alternator, which is trying to charge the battery, and tells the light to go off. This is not normal on a vehicle with an alternator. You need to have the alternator checked as it more than likely needs replacing.
One of two things is normally wrong. Either the battery has a dead cell and will not accept a charge, or the alternator is defective. With the engine running at idle check the voltage at the battery with a digital voltmeter set to the 20 Volt DC scale. If the alternator is good you should read from 13.5 to 15.5 Volts. If the alternator has a separate drive belt then it is possible the drive belt is broken.
Maybe the battery is defective. Check the voltage at the battery terminals with the engine running at idle. You should get 13.5 to 16 volts. If not the alternator is defective or the voltage regulator is bad. If you are getting the correct voltage, the battery is bad or the connections are corroded.
Turning the lights on put a load on the alternator causing the idle speed to drop. I would have the battery and charging system tested to make sure everything is okay. The battery may be on its way out.
It is the Alternator. use a voltmeter an check if voltage with engine running is arrounnd 14v or more. than it s good. if voltage below 14 bad alternator.
That would be the alternator, voltage rgulator, or even a bad ground. Email MYCOMATT167@YAHOO.COM follow up