I was driving my car today and the radio shut off by itself. The dome lights were dimming also. I checked the battery, its pushing out 13 volt and its also charging. So what could it be? Alternator? or the battery? Thanks for ur help

 

check a fuse would be a good start

BTW, what do you mean by dimming dome lights? - I believe there should be just one dome light unless you are driving something else but maxima ...

 

13 volts is insufficient charging. 13.8 is the minimum you should see coming from your alternator 14.2 would be right

 

You should also check your battery terminal. That use to happen to me with my first car and there was a problem with the terminal.

 

He was talking about 13v out of battery, which is not bad at all.
I assume that battery would not be quite alive running without alternator, right?

 

13V on the battery is too high. the bat should be 12.6

 

My red optima shows 12.9V all the time and 13.6-14.2 when charging (I have a voltmeter on the dashboard in my truck)
And no complains so far ...

 

when i got my gxe the radio would shut off when i would give it a lot of gas. the problem was an overcharging alternator. take it to an autozone and they can tell you if the alternator and battery is good or not.

 

well i checked the fuse and everything and they all seem right. I just checked it b4. It was at 11 volt and then its start jumped up to 13 which its normal. But when i started the car its seem didn't wana start. Well, i'm getting a new battery today and see if it solve the problem. If not then i will get the alternator. I killed this battery so many times, so u think it could be a reason to cause this? thanks

 

before you spend $100 on a new battery, look at your cables. it's often the problem- especially if you're getting 11v with the engine off and 13v with it on. Check for a tight fit, and a good connection to the battery. also make sure if you're using the crappy factory connectors that they're not falling apart. shortly after I bought my SE, I had the same problems. battery tested good (I even swapped it with a known good), but it still wasn't starting. turned out to be the factory connector was so corroded, there wasn't enough metal there to conduct enough current to start the car.
put some new connectors on it and I was good to go.

FYI, at idle 13v is perfectly fine for an alternator.. Mine was actually down at about 12.6V at idle, but still putting out 75A of current.. raise the RPM to 3000 or so, and it was putting out 98A at 14.2V. still close enough to factory specs to me!

 

When you try a new battery don't start the car yet - just see if other electrics work (including radio). If not, don't blame an alternator.
Something else is coursing a problem (like bad battery terminals).

Talking of the radio - I would check if it has "power", because it should operate even with 11v (one wire is for memory - always has power; and another wire powers your unit but only when key is turned).