So I had the alternator and the battery tested. Both are relatively new and everything is within spec. Tension on the accessory belt is in spec. It doesn't matter what rpm the engine is running, the dash lights and headlights all flicker at the same rate. The only thing I can think of is a bad ground connection to the chassis somewhere? It's been getting progressively worse over the past year. Google keeps telling bad alternator/battery, but after taking the car to Advanced Auto I'm a bit clueless.

7/12/2012 11:24:18 PM

i wouldn't trust most of the dumbfucks at advance auto as far as i can throw em

7/12/2012 11:26:43 PM

Is it pulsing or truly flickering randomly? Pulsing is telltale alternator/voltage regulator but flickering could be bad grounding somewhere. Wiggle/check your underhood and/or underdash fuse boxes for corrosion or poor connection.

7/13/2012 12:12:21 AM

^^ Well they hooked up the diagnostic to the battery and the charge rate was within 5% of the alternator's specs, as was the battery. Battery is 4 years old, alternator just under 2. I don't know how they could mess that up.

^It is more of a pulse. I'll test the voltage regulator this weekend.

[Edited on July 13, 2012 at 1:15 AM. Reason : .]

7/13/2012 1:14:46 AM

Quote :

"I don't know how they could mess that up."

yeah, me neither, but they do.

7/13/2012 1:58:31 PM

With the car on, the battery terminals are reading 15v. Doesn't matter if at idle, or reving to 4k rpm. 15v all the way.

With the car off, the battery was at 12v.

Unfortunately, I don't have a decimal spot on my multimeter for DC voltages (it was a free multimeter :betup: )

I think I have another one laying around that does read to the decimal spot.

7/22/2012 12:51:05 AM

my dakota did the same thing. headlights and dash lights all flickering together. i had a burned-up headlight switch.

7/22/2012 10:04:48 AM

^ Interesting. How'd you end up diagnosing that?

7/22/2012 2:23:22 PM

^probably because his dash lights were flickering, too.

7/22/2012 2:31:47 PM

it was the pull-out style headlight switch and i could wiggle the knob around and get them to come on and off

7/22/2012 2:42:00 PM

Do the lights pulse or flicker when the engine is off? If yes, bad ground or bad switch. If no, it is most likely the voltage regulator. Get a real multimeter and test. Check the voltage of the battery with the car off, voltage at the battery when the car is running. If you can get to the lights, you can test the voltage at the lights with the engine on/off. Can you try turning on just the dash lights without the headlights being on? If so, do the pulse when the headlights are off?

Sounds most likely that it is a voltage regulator. It is most likely built into the alternator and you will have to replace the whole alternator. Get one with a lifetime warranty and be done with it. You can always just go buy an alternator and pop it in, if that doesnt fix the problem, take it back.

7/23/2012 9:19:11 AM

YEAR MAKE MODEL

if its a chevy truck, its the voltage regulator in the alt.

7/30/2012 4:15:35 PM

OH, it's definitely the alt. I was testing it and happend to see it spike to 20v at 4krpms. LOL. But then it went right back to working at 15 volts. Odd that 85% of the time, it functions 100%.

7/30/2012 10:29:27 PM

^
I laughed

7/31/2012 3:11:59 AM