Alternator charging low? Please Help!

[doctah-jay]

Whats up guys been a while, just when i thought i was done with electrical problems one appears. I changed my alternator yesterday, my car needed to be jumped for the past week. My battery is less than a year old so i don't think it is the main problem. I used my voltmeter on my battery while the car was running and saw that the alternator was only kicking out about 12.9. When i get a jump the battery reads 13.6. So i had another alternator laying around went to advance auto got it tested and they said it was good. Next day i swap it into the car. When i got another jump, the car the alternator still reads 13.0. I drove it around maybe thinking it had to charge the battery and it didn't change. Iv searched a lot and the most i can find is something about a voltage regulator fuse/wire. I was wondering if anyone knows the location of this fuse because so far nothing is specific. I also read the fuse able link is the fuse for the regulator but it didn't look blown to me. My battery is on when the key is in the own position, and goes off when the car finally cranks so im confused there. Any help would be appreciated. thanks guys. car-1990 240sx hb motor-1992 trans-manual

[doctah-jay]

Update: i moved my car into the garage and after i did that i checked the alternator voltage at the battery to see what it says and it said 13.3. i had my friend turn on the lights and it dipped to 13.1 then when he revved it the voltage went to 12.9. im not sure why the volts arent going up.

[PapaSmurf2k3]

I thought the voltage regulator was internal to the alternator itself.

If your battery is causing a drain, you could try disconnecting it (with the vehicle running) and seeing what the voltage is. Just be careful you don't arc the leads out somewhere.

[doctah-jay]

Thanks for responding, i thought the same thing about the regulator. But i guess there is a wire/fuse that from the regulator that lets the ecm know when to ramp up voltage. I guess the wire could be damaged or the fuse popped but the fuses i checked looked fine and it didn't appear there was any damaged from the wire that plug into the alternator. il try and get it jumped again today to see what the voltage is with the battery taken out.

[doctah-jay]

i did what you said and with the wires off, the alternator was doing 14.+ volts. when i put it back on the battery it went down to 14.1, then when i drove it back into my garage the battery stayed at 13.8 with the lights on. so now i have an over voltage problem? something isn't sending the right information for the right amount of voltage, and it don't think it is the alternator because advance tested the extra one had out of the vehicle.

[PapaSmurf2k3]

13.8-14.5 is pretty normal operating voltage.

[doctah-jay]

yea i understand its normal, and i wouldn't think anything of it, if it wasn't only happening after i took the battery out. when i jump it with the battery connected it doesn't reach pass 13.1. im finally able to check the battery tomorrow to see if its pulling a lot of voltage.

[PapaSmurf2k3]

I thought you said it was 14.1 with the battery connected and everything... that should be good.
If your battery doesn't hold a charge long, you've either got a bad battery, or you have some kind of power draw with the ignition off.
You can remove a terminal and put a multi-meter in line between the battery and its respective terminal to measure amperage. You shouldn't really see above .06 amps after the initial spike to energize the ECU capacitors and whatnot (~12 seconds or so).

[doctah-jay]

oh no, it was 14 and plus when i had the battery out and tested at the terminals, and it did stay above 13 when i put the battery back in with the car on. But as soon as i try and start it with everything connected the voltages dont go above 12.8 barely 13. i got the battery recharged yesterday but the voltages dropped to 12.4 that was before i even put the cables on the terminals. i dont want to buy another battery yet because if the alternator still cant recharge it to 13.6 then im going to kill another battery. I cant recall ever hearing of a situation where the battery didnt hold a charge so much that it didnt even meet the alternator volts but i could be wrong. by the way thanks for helping me out papasmurf!!

Not sure if this matters but my car was an auto at one point, but the person i bought it from changed the motor to a dual cam and the trans to manual. not sure if this problem is a common one amongst swaps.

[PapaSmurf2k3]

So let me get this straight:
Alternator outputs 14+ volts w/ no battery
Battery reads 12.4 volts after sitting for a while (unclear if you mean its been connected to the car or not... need to clarify this)
System voltage (just starting off with the battery connected) is about 13 volts

Honestly it sounds like the alternator is working more or less OK, and you have a bad battery or some kind of draw that is killing the battery prematurely. If the car continues to run without the battery connected, generally the alternator is good.

[doctah-jay]

yes to your first statement.

to your second question i got the battery recharged at auto zone yesterday at about 4pm and using a voltmeter today at about 12pm it was 12.4. when i connected my cables to the battery after using the voltmeter it was still the same volts nothing was pulling volts with the car off.

and yes to your third question, the volts barely go above 13 and usually stay around 12.8 and with lights on and revving it stays/drops to around 12.8.

i guess il try a new battery, its my first time dealing with a recharging problem that a new alternator didnt fix. especially when the volts dont rise with any load and stays in one place.