when im idling,my volts stay around 9-11(dash guage),but when i shut the car off and test the battery,i get 12.4 volts. (i used a volt meter on the battery). its hard to start,like the battery is low or the alternator is going bad. but when its shut off the battery shows 12.40 what is wrong here?

 

Is there any corrosion around the battery terminals? if so that could cause the problems you describe.

Also, I believe you should get more than 12.4 when you test your battery. Anyone wanna second that or correct it?

 

Car electrical systems are 12 volts. Amperage is where it differs from system to system.
EXAMPLE:
The main circuit in the car is an 80 amp system. The radio/audio system is a 20 amp system. If either system exceeds their rating, they will blow their fuses.

I know that the average RX7 runs 12-14 volts while running. Take your car to AutoZone/Advance Auto/whatever and get your alternator tested. If it checks out, do the same with your battery. Best of luck to ya.

 

12.4 V sounds right for the battery. Most cars, in general, charge at or around 14.4 V. When your at idle, are your lights on? stereo kickin? doesn't sound like its your alternator cause it's not a factor when starting your car, and if your battery's around 12 v, it sounds like it's charging corectly. so what do you mean hard to start? not turning over as quick as it should? try an auto supply store, they can test your battery and alternator to make sure.

 

So...since you have a voltmeter, why in the world don't you just idle the car and put the meter on the alternators output? Should read approx 13/14 volts. If it does, then put the meter on the battery and see if the voltage is approx the same. Report back, Hup, two three four.

 

ok,sorry it took so long to reply back,but i am having trouble starting,and when i turn on the lights it kills the volts to death,even more so the more stuff i turn on.i didnt know i could test the alternator like that,ill go do it now......

 

ok here are the results,idling with nothing on,the batery reads 12.3-12.4,and the alternator reads 14.5 or so,with everything on inthe interior,like radio,heat,lights,the battery reads 10,and the alternator reads about 11.5-12,could this be my battery not be charging right,or could i have a week alternator?