Bad Alternator Or Regulator?

[amnash]

ok so here is what i have going on. the battery hold a solid 12v its 1 year old red optima so its good. Everytime i start the car its struggles to turn the starter and then slowly picks up speed and then the engine will just barely start. today was bad as i was stuck in a parking lot for 15 minutes until it decided to start for me. no im going to fix it before it gets worse.

once the car is running here is my voltage at battery with different things turned on;

car off : 12.14v

running : 12.78v

+ two 12" electric fans wired straight to battery, those turned on : 12.00v

+ headlights on : drops to 10v then rises slowly to 11.30v

+ music : 11.30v

+ heater with blower on max : 9.96

the fuel pump is also wired to 12v constant. i haven't dealt with alternator issues before so this is a little new. isn't there supposed to be something keeping it at like 14v while running regardless of how much electronics i have turn on??? or do i just have to much electronics?

so is this just a matter of changing the alternator? or do i need to upgrade something somewhere?

[amnash]

also, because my voltage is dipping and jumping around its making my fuel pressure inconsistent

[speed]

Looks like it's a bad alternator, when off should be reading around 12.4 and on 14.7,try testing the alternator first

[amnash]

ok i will get it tested. and it should stay and 14.7 even if i have all my electronics on right?

[speed]

Yes! 14.7 will tell u that ur alternator is still charging, and if it's reading 12.3ish around that while the car is on then that means its running on your battery!

[amnash]

i didn't check the voltage while cranking.. what should it be?

i just went ahead and changed the alternator, i had one sitting in the garage from my rb20.

after the install:

car off : 12.14v
running : 14.08v
+ two 12" electric fans wired straight to battery, those turned on : 13.81v
+ headlights on : drops to 10v then rises slowly to 13.64v
+ music : 13.59v
+ heater with blower on max : 12.80

so it is a lot better. i hope that my starting problems go away. my battery light is off now too

last question though.. the voltage is still dropping with all the accessories on. isn't the output supposed to constantly change to maintain a 14.7v charge???

[future_R34]

Alternator can only pump so much juice at a time, my guess is the battery has been ran down so many times that there is no CCA's left. Get your battery tested, most places do it free

[Rblove26]

If your voltage is still close to 13 with all those acessories on its doing pretty good lol, seen how your battery has already dropped down a few times before from starting and running with no charging it may take a while for your battery to come back to 100% if it even ever does. also alternator can only put out so much amperage and depending on the draw from all your accessories it might just be breaking even. try giving your battery a nice low amp charge for a couple hours to help bring it back

also, when your checking to see if an alternator is charging or not, dont always just go by the voltage because you may see 13-14 volts but only putting out 30 amps, and come time for a high current demand it wont keep up.

hope this helps and glad to hear it was just the alternator (usually is lol)

[Nvdgtr]

my car is doing this as well.. Im going to test the batt w/car off then w/car on and see what it says. Any write ups on alternator replacement? or is it pretty straight forward, remove old then install new!

[amnash]

ya its very simple. one mount bolt. the tensioner bolts and belt.

so when i did the rb25 neo swap in my r32 i notice a wire from the ecu pin 78 (electric fan relay control signal). so i thought i could use this with a relay and rewire my fans so there was less drag on the alternator.
so with a test light hooked up between that wire and + terminal i idled the car and let it warm up. it go all the way up to 200F and i pulled the plug, turned on the fans and it dropped down to a normal 180F
so im not sure the purpose of that wire from the r34 ecu. the neo did have a clutch fan on the water pump anyways...so i dont know.. was there also an electric fan on the r34??

so tomorrow im gonna buy one of these and then just have it so that at 200F the fans turn on with full 12v. that way, the only time they are actually on is at a long red light or reall slow traffic. most of the time they will be off

[Nvdgtr]

Well tonight I used the volt reader.

With car off it read: 12.48
With car on it read: 14.09

this time the car started fine, could it be the starter is starting to be on its way out? it has been sluggish before. like it was hard to turn over...?

Thanks!

[amnash]

the car is still really hard to start. im going to check the voltage when cranking and then change the starter with a rb20 starter i have sitting around. does anyone know a north American vehicle that has a starter that would work? would be nice to have a nice new one in there. im tired of this sluggish starting it makes my car look like it runs like **** but it doesn't...

what you the voltage be when cranking? and if the starter doesn't fix it what should i try next?

[amnash]

ok so the voltage while cranking drops to like 7v....i changed the starter for the one i had laying around and there was no change. maybe its the battery

[Voodoo_ChildR32]

Dropping to 7 volts is battery, you want at least 10.5 volts or more.


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[amnash]

damn. its a friggen optima too. i guess i will go buy one, wait a month and then take the bad one back :P