charging problem!

okay I'm having quite the dilemma here. My 2002 2.7 has got me stumped. I went and started it on Monday and the battery light was onso I tested it and I was getting 12 volts to the battery and 19 volt off my alternator .so I figured hey my alternator must be bad so I went and got another one.I put that one in and it does the same thing. so I figured hey I might have got a bad alternator so I took that one back and got another one but before I put that one in I had it tested and it tested perfect.so I put that one in thinking hey this will solve my problem but nope. still only getting 12 volts at the battery and 19 volts off the alternator. so then I figure hey I MUST have a bad ground wire somewhere so I pull all the wire loom out check everything and all my grounds and clean them up and put them back, and it still does the same thing. so for shits and giggles I put a new battery and also because my other one was still under warranty and they still didn't fix anything. then I dug a little bit deeper and found when the vehicle is not running I get 12 volts at the battery and I have 12 volts at the fuse for the alternator but when I put the wire for the alternator back on the alternator after I take it off it drops down to 7 volts at the fuse but still 12 at the battery. Im stumped where to go from here.

 

how are you measuring voltage? 19 volts seems VERY unlikely

 

I know thats what i thought. I'm putting the negative on my volt meter on the negative battery terminal and the positive on the post on the alternator where the wire hooks to it that sends power to the battery.

 

try your meter on the battery posts with the truck running

 

Did that to it stays around 12 volts

 

should be reading at least 14 volts at the battery with truck running

 

yeah I know that that's why I'm trying to figure out why the voltage is not getting to the battery.

 

http://www.tacomaworld.com/forum/1s...nators-1-new-battery-no-luck-1997-taco-2.html

 

Fill in the blanks for me:

1. Truck off, use volt meter on +/- battery posts volt = ????
2. Truck on, use volt meter on +/- battery posts volt = ????
3. Truck on, positive lead on volt meter on alternator post and negative lead on meter on battery negative post volts are = ???


Also this is a good read:

 

1.) 12 volts
2.) 12 volts
3.) 19 volts

 

Okay and your measuring at the alternator not at the fuse box correct?

if that's the case I put my money on a bad alternator. Even "new" re-manufactured alternators can be bad straight out of the box. Could be a faulty voltage regulator which is internal on the Tacoma alternator. I say return the alternator and try again (I recommend NAPA over all the others). Hopefully that 19 volts hasn't destroyed your battery..

I had charging issues a while ago and had to replace my alternator 3 times before i got a good one.

http://www.tacomaworld.com/forum/1s...995-1997-alternator-charging-issues-read.html

 

yep I'm measuring at the alternator. the thing of the whole matter is all three alternators have shown the same result and the one that is in there now is from napa and they tested it on their machine before they gave it to me and it tested fine.

 

if the alternator is putting out 19 volts something is wrong with the alternator, have you tested at the fuse to see if you getting 19 volts there?

 

yep I tested it at the fuse to were the wire comes into the fuse box from the alternator I have 19 volt but on the other side of fuse I still have the 12 volts.

 

Have you checked your cables? Additionally there is a 120A fuse/breaker in between the alternator and the battery from looking at the wiring diagram. Have you checked in you under hood fuse/relay box for anything labeled "ALT"?

To me it sounds like the charging voltage from the alternator is not making it to the battery. Have you measured from the negative post to the alternator positive lug with the engine off, key on?

 

Test that fuse for continuity. The fact you have voltage differences between each side indicates it may be open.

 

Yes i checked the cables and they are fine. I havent tested the alternator and the neg. battery terminal with the truck off but the key on yet. also I tested the fuse because you can pop the plastic cover off it and it reads 12 volts with the truck off. the odd thing about this whole thing is is if I unhook the wire off the alternator and I put my volt meter on the post in the fuse box that goes to the alternator I get 12 volts but soon as I touch the wire back on the alternator it drops to 7 volt.

 

How would i go about that

 

There is a voltage regular in the system somewhere, that is probably the culprit. There are sometimes part of the alternator, and sometimes serparate. If you alternator is testing fine, I suspect your voltage regulator is separate. One diode gone would drop your voltage to 12v

 

Thats the way other odd thing the only regulator that I could find that would be part of that is the one that's part of the alternator.