What does it mean when my battery gage goes from the middle to low all the time Auto zone told me my battery and alternator r fine
You mean your volt gauge. Turn your key to on with the lights off and see what the volt gauge reads. If it reads what what you are refering to "low" as then that's fine. That will be around 12 volts which is normal battery voltage. The mid range reading is when the altenator is working and shoud be close to 14-15. A little higher or lower is alright. If your saying that it is dropping out I would say that your altenator is slowly failing. You can try to clean the wiring connections, but I would bank on it going soon. Remember if the gauges drops to battery voltage and doesn't come back up you will only have a limited amount of time before the battery drains and the engine dies.
Could be a gauge or wiring problem to the gauge, check the battery cables for a good connections.
As long as the pointer is somewhere in between the two hash marks on the guage you should be ok
To verify the actual voltage to confirm that you gauge is correct read the voltage across your battery with the engine off and when it's running (altenator working) with a multimeter. I will stick to my first comment. In my experiences it is almost always the altenator that causes fluctuations with the volt gauge, second is loose/damaged wires. If the gauge goes high (rare) or low and stays there then it's a gauge/cluster issue.
The regulator controls how much voltage the alternator puts out. If it is dropping the regulator is going out. Which means you need an alternator. Have it checked again with everything on. High beams, wipers, radio, turn signal and see if it will drop out.
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