I just need some guidance on what does what and where I should look on fixing the issue. When rolling down windows or turning on A/C, I can see my RPMs drop and headlights and interior lights dim. I understand this is pretty normal when it comes to cars and makes sense. I want to know what could be the fix/upgrade in fixing this.

I was searching through this forum and throughout the web and now a bit confused on what does what. From what I understand, battery is only there to start up the vehicle. A lot of people say upgrade the battery and it will fix the lights and what not from dimming. Isn't it the alternator what you would want to upgrade to ensure no dimming since it's the one creating the electricity?

 

No, not normal at all, happens, but not normal

Most likely you have a bad field in the alternator
Alternators use 3 Field Coils(in outside case) to generate AC volt electricity
Each Field has 2 Diodes that convert the AC volts to DC
If a field, or diode on that filed, fails then you lose 1/3 of power generation

Alternators AMP rating is based on engine running at 1,800rpms
At idle RPMs, say 800, they output about 60% of rated power

So a 95amp alternator produces about 60amps at idle
Which is fine since most vehicles only need about 45amps with EVERYTHING on, lights, heater fan, windows going up and down, AC on, ect........

But if you lose a Field then at idle you have 40amps, not 60amps, 1/3 less
So with everything on lights would dim anytime you added more amps, i.e. window or AC fan, or AC compressor coming on since that can slow idle RPM, so reduce alternator power a bit more

And this is why you don't notice this dimming when driving because engine is above say 1,500rpms and AMPS are higher than 40

When you come home from driving more than 15 min, DO NOT SHUT OFF the engine
Turn every thing electrical off, and open the hood
Test battery voltage, engine is idling
Should see 13.5v(min) to 13.8volts, remember it
Now turn on all the lights, door open, Fan on HIGH
Retest battery volts, should be EXACTLY the same voltage as before, if its lower you have a bad Field, you can drive this way for years, because most of the time you are above 1,500rpm so battery gets charged and everything works


No car maker specs in an alternator that doesn't have enough AMPs to power everything at idle RPMs, no reason to, so dimming lights at idle means something is wrong with alternator
Which is why its not "normal", but happens, lol

Battery's only purpose is to start the engine, car batteries are 12.3v to 12.8volts, new might be 13.0v
Alternators MINIMUM voltage is 13.5volts
So once engine is running all electrics run from alternator, and voltage travels TO THE BATTERY to keep it charged for next start up

 

@RonD Hey, thank you so much for the detailed response. Learned a lot from that one post that I did from my own research for hours.

I don't know if the same method applies but I have a live monitor that's connected to the OBD2 and I have display set for voltage. While drive, I see an average of 14.00 and it drops randomly in the high 13.00.

I parked the car running and then turned everything on such as lights, A/C and rolled down the windows and the voltage dropped down to the low 12.00 and worked itself back up to a low 14.00.

I'll test the battery with my voltage meter tomorrow once I get to work.

 

Your voltage regulator is most likely the issue

Voltage regulators in alternators/cars are pretty simple

First, an alternator works by the voltage regulator supplying the rotor 7.5 to 9volts(approx.), this creates a magnetic field around the rotor
As the pulley spins the rotor, this magnetic field creates AC voltage in the 3 Field Coils in the case of alternator, this outputs 13.5 to 14.9volts depending on what the rotor voltage is, 7.5v to 9v
So mechanical spinning of the alternator gains 6volts(approx.), i.e. 8 volts IN, becomes 14volts OUT

There is something called Electromotive Force, when you turn on a light and the light comes on then the power consumption is now equal on both terminals, in this case positive and negative, there is flow and "pushback", meaning flow is set no more power is needed, pushback from the light bulb prevents more power from flowing thru it
If you turn on another light, pushback drops and more current/voltage is needed until its lit and pushback comes back, both bulbs are lit and no more power is needed

Voltage regulator uses Pushback
When you first start the engine the battery is drained
So pushback is low, voltage regulator should be at 14.5v to 14.9volts
As battery recharges, say after 5min of driving, you should see under 14volts,13.5 to 13.8volts, because battery is pushing back, its fully charged, all there is is the Vehicle system's power use
When you turn on lights pushback drops voltage regulator responds, so voltage may drop but come back to say 13.7volts in 1 second, doesn't take that long

Running at 14volts or higher can "cook" a battery long term, some newer batteries like 14volts, lol, but regular batteries like 13.5 to 13.8volts
And at NO TIME should it drop under 13.5volts with engine running, that would indicate a problem with the system