My car when at the light my batt meter goes down an then when I take my negative batt cable off it revs up an down up an down then shuts off I was told it could have been a ground from when the put transmission in

 

Check what your voltage is at the battery with a good multimeter. At idle, and just off idle. Should be somewhere around 13.5 - 14.3 volts at idle.

 

Running your car with the battery disconnected is not a good idea and is not a good trouble shooting method. I'd second Notch's recommendation, and add to it. Check the voltage at the battery posts and at the battery-they should be the same. Then use the engine block for the negative meter lead and the battery terminal for the positive meter lead. Let us know what you get.

 

Roma drop to almost 0 when ac is on an it's a new battery hope it's not something major

 

My rpm sorry about that

 

Just to clarify, turning on your AC will cause your engine RPM to drop almost 0 ? Meaning its barely running ?

You'll need to check voltage as stated above, that would rule out the alternator. Let us know what that voltage is.

 

Yea when it comes on it drops below the line above 0 an then comes back up to normal an keeps doing it every time it kicks on

 

At idle it's at 13.45

 

With ac on it is at 13.12 an drops 12.97 then goes up an with lights an ac it's at 12.4

 

That's barely acceptable, but should still be fine. Just know that at idle with the air on, the battery is not charging. It's not discharging, so that's OK, but I like to see 14+ volts at idle. Then you'd have 13+ volts at idle with the air on.

Maybe check to make sure your cables are clean and tight , then if it really bothers you, upgrade the alternator. A little extra juice never hurts......