AC Idle rpm question

[DSG2003Mach1]

Should idle rpm increase when the AC is running or should it be the same rpm as when its off? My 03 Mach1 seems to idle in the same rpm range AC on or off. It has mild cams, I usually see the aeroforce RPMs bouncing around from 830-870 either way.

I've got an aftermarket alternator and just wanna verify before going back to the alternator manufacturer again. If I let the car sit at idle and turn on the AC and lights voltage crashes into the low 12s. I dont know if the rpms should be bumping up a tad and they aren't or if its a messed up alternator.

 

[01yellercobra]

The RPM should stay the same with the A/C turned on. I'd say your alternator is having issues.

 

[decipha]

the idle bumping up with ac is dependent upon the tuner and if they wanted to or not.

Idle voltage should drop with ac on at low idle. Low 12s are perfectly normal and fine.

 

[DSG2003Mach1]

the idle bumping up with ac is dependent upon the tuner and if they wanted to or not.

Idle voltage should drop with ac on at low idle. Low 12s are perfectly normal and fine.

What voltage at idle should be a concern then? Or what range would be normal at idle with all the accessories going?

I admittedly never really watched them on the gauge prior to getting the alternator. Before changing pulley sizes there was definitely a problem as it sank into the 11s and was still falling. I never let it see how low it would go for fear of not being able to start the car if it stalled

 

[decipha]

ideally you always want 0.5 volts more than the battery voltage while the engine running. So if the battery sits at 12.2 volts with the key on engine off you want it at least 12.7 volts minimum while running ...ideally.

However if you have your ac on head lights on radio on and idling its common for voltage to drop down there in the not ideal area. Once you put some RPMs on the alt though it should jump up over 13 volts easily.

 

[DSG2003Mach1]

ideally you always want 0.5 volts more than the battery voltage while the engine running. So if the battery sits at 12.2 volts with the key on engine off you want it at least 12.7 volts minimum while running ...ideally.

However if you have your ac on head lights on radio on and idling its common for voltage to drop down there in the not ideal area. Once you put some RPMs on the alt though it should jump up over 13 volts easily.

any time I'm driving its 13+, just sitting at a light it'll be in the low 12s. with em both going

 

[decipha]

yea thats common no cause for concern