Nissan Repair: everything is dimming when i use any kind of power.., battery cables, electrical expert

Question
QUESTION: i have a 98 maxima and recently had my alternator and battery changed, but still everything is dimming when i use any kind of power...such as power windows, brakes, turnsignals everything. It dims to the point that sometimes my batterylight and airbag lights will go on and then go away...my mechanic does not want to spend the time to look at it anymore and im thinking about taking it to a electrical expert, but wanted to see if i could save some money and fix it myself first...thanks for your time

ANSWER: Steve,

The system sounds like the alternator is defective.  I would go to Autozone or Checker and get a free electrical inspection.  The car should put out 13 or 14 volts when at a high idle.

---------- FOLLOW-UP ----------

QUESTION: i did go to autozone already and they said the alternator is fine...when you said to get a electrical inspection...is that just the alt and battery? any other ideas what the problem might be? thanks for your time again

Answer
Steve,

You might have had a bad insepction.  What I am saying is that if the system dims when accessories are turned on you are not getting enough power.  Now, the alternator and battery could be fine and something in the car is causing an excessive load.  But, the only way to know for sure would be to start disconnecting systems, one at a time, to see if one is draggin the system to its knees.  You should get a multi-meter to do the testing and that way you will know what it is.  Checking the car, running, the battery terminals should read around 13 to 14 volts.  If you are at 12 volts you are not getting enough power.  Check the high amperage items like the blower motor, headlights, compressor and electric fans first.  These are the usual suspects.  Also, if the battery cables are worn and corroded they will limit current flow.  Check these and email me back.