charging problem!

By measuring the resistance (ohms). A good fuse will have zero ohms, a blown fuse will have infinite resistance. Also, a blown fuse should be VISIBLY bad, with a break in the 'wire' inside.

 

I did visibly check the fuse for the alternator 120 amp on fuse box and it is fine and then I check the other fuses in the fuse box and they all tested fine

 

hook jumper cables from battery ground to engine ground and battery power to alternator power lead in terminal and then it will work.

the alternator puts out max power when it cant find a battery connection so the power lead to the alternator is bad. this is why you don't want to run it with the battery disconnected or it send too much power through the electrical system. this is the only explanation for the symptoms you have, a bad positive battery connection or a bad ground to the alternator.

my bet is the power or ground wire to the alternator is corroded somewhere between the battery and alternator

 

see I thought that too. I thought that wire was bad but then I unhooked it off the alternator and left a hook to the battery and its still putting the 12 Volt through it when I put my volt meter on it making me believe its still good. I also went through and cleaned with 80 grit sandpaper the ground from the battery to the block and then from the battery to the chassis and every other ground I could find.

 

corroded wires will still read voltage even when they don't let amps flow through them, it confuses a lot of people because as you say it shows volts and it would even show ohm continuity but as soon as you try to draw power for something you get nothing

 

See i did not know that guess it can't hurt to throw some wires out of considering the truck is 12 years old and has 225,000 miles on it.

 

another note is this happens internally to batteries too and that is why you must load test them to be sure they are good and not just check voltages

 

If you can, perform the test again where you have 12V, then make a connection and get only 7, but take a photograph so that I can see exactly what you are doing. 19V output from an alternator typically means that the alternator is not getting the correct voltage information to the internal regulator. (EVERY Tacoma has an internal regulator in the alternator, NONE have external regulators) this can quickly damage a new alternator if not corrected quickly.

 

yeah i'll try to do that tomorrow when i'm working on it

 

UPDATE: My truck is fixed.
I changed out the wires going from the battery to the fuse box, then from the fuse box to the alternator. Put a new fuse in the fuse box for the alternator even though it tested fine. Ran a new ground from the battery to the block. Then i did the extra ground wires from the battery to the frame, to the intake, and to the fire wall. Im just assuming that one of those wires must have been bad since the truck is running and charging like a top now.

 

glad its fixed but its a shame you did all that and now you still don't know what the real problem was because it could be any of the things you did.

my bet is the most likely thing was just a bad ground connection doing it

 

Im pretty sure it was a ground to the block or the wire going from the fuse box to the battery. Because when i pulled them off both of them seemed to have a break/weak spot in the wires. Yes they did test fine but whos to say that it was together just enough to make a weak connection. as far as doing all that work I figured it was just maintenance anyway because everything was pretty old and it sets me up for when I want to put a winch and everything else in there because all the wires are heavier gauge now.

 

yep, if something looked funny with the wires they were probably both internally corroded. even if only one was the problem the other was likely not far from failing too.

its just rare for me to see a harness go bad unless its melted from shorting

 

well it wasn't the harness it was the 6 gauge wire that comes out of the fuse box and connects to the battery. But yeah i agree with you that a harness should never go bad unless it gets melted or there's some kind of corrosion in it.