It doesn't seem to be alternator

i have a 2001 4runner that has quit running on its own. I thought it was the alternator but when i went to buy a new one we tested it. It was good on testing. so we went home and replaced with one off another truck. Still the same problem. we replaced both battery terminals hoping.
The 4runner will start fine if jumped off but soon cuts off from low battery. ( about 2 to 5 minutes ).
None of the dash electric works. radio, ac, none of the gauges. we searched the fuses and replaced the main power 30 amp under dash. it had some corrosion but looked solid.
we checked voltage from the alternator and it is jumpng from 6 to 12. Never the 14 we expected.
I am going back out to charge the battery and try again tomorrow. Has anyone had something similar happen?
thanks just a farmer

 

Welcome to the forum, do know the condition of the battery?

 

On the charger now. Not certain its good

 

Fully charged battery, cranks fine but gauges etc still dead.

 

If the battery is bad, it will not provide enough current to the alternator to create the electromagnetic field in the rotor coils. With no magnetic field present, there will be no current produced (a conductor passing through a magnetic field produces current in the conductor).

https://www.howacarworks.com/basics/how-the-charging-system-works

 

The battery held the charge all day but weakened by the end of the day. Retested the alternator at auto zone while running. Putting out only twelve amp but we hope it's in the ground. Haven't checked yet. still open to ideas.

 

We changed battery but still no change. we have changed the alternator. The only thing i can think of is checking the ground wire at engine block which i checked. So tight i wasnt able to break it loose yet.

 

Fixed it. I know we checked fuses with a meter. All were good. Remember the gauges didnt work on dash? I went back and pulled it. The fuse
Looked good. Then it crumbled inside. Replaced the fuse for gauges and alternator and dash work. That was so easy it only took hours for a one minute fix. But im a farmer.

 

Don’t let it get you down. Fuses can look good, but can develop a crack that opens the circuit without “looking” like it’s blown. Only sure way is to use a 12v automotive test light and check both sides of fuse. If light lights on one side of fuse but not the other, the fuse is bad. If it doesn’t light on either side, then the circuit is not energized (probably by design).

Test light is also handy for checking other automotive electrical.

https://www.googleadservices.com/pa...wiDhbamirbnAhVxGTQIHdUjBQYQwg96BAgLECQ&adurl=

 

Persistence and a good testlight goes a long way!!
Good Job!