Alternator will not charge car

[TomFraser]

I have a tested and working alternator in my car

I have a brand new battery in my car

I have a turbo timer that is hooked into my ignition power that doubles as a voltmeter to find voltage (I know it is not the most accurate, but I just need to know about where i'm at)

I charged the battery to full and ran the car for a day, In the morning I was only around 12.6 volts, so I knew something was wrong, on the way home I was driving on 9 volts and just made it, the alternator did not charge the battery at all, I was just draining the battery.

If it was the alternator fuse then the car would not start right?
my engine and charge fuse are both fine.

The alternator is hot, almost too hot to touch when the car is off, is this normal?

what should I check next?

 

[hvyman]

what is your voltage output from the alt to the battery( with multi meter)?

 

[tlo86]

check the supply + ground wires ive seen them corrode on some cars to affect the voltage. especially with grounds to the chassis and not the block

 

[92nsx]

Yep check voltage at battery with car running (should be 13.6 or higher IIRC) . Then check cables and ground to block (maybe even ohm out the cable running from the battery and the alternator) If it all checks out then Im guessing your alt. is shot.

And, Yes, if the ALT fuse if blown (100A fuse) you car will not start. At least mine didn't when I accidentally touched the alt. cable to the frame of the alt.

 

[radiod]

Yes, voltage should be 13.6V at least....14.4V is optimal. And no, it's not normal for your alternator to get hot...I would lean towards the alternator being pooched. Test it first though, make sure the wiring is all done up properly. If you doubt your own tests and don't mind spending some cash, most auto parts stores and alternator rebuilders will have a test bench they can test the output on.

 

[TomFraser]

alternator just tested works fine, voltage at battery starts as high as 12.6 then as I drive it goes down.

I can charge the battery buy putting positive on the alternator's positive terminal, and ground on the actual alternator so I know they are connected.

I'm going to go tighten all the ground bolts now

 

[Pernilongo]

Found the problem!!!! the alternator is not suppose to charge your car, so you have nothing to worry about. the only thing it charges is battery. :biglaugh:

 

[Who]

I

what should I check next?

Check the alternator again!

Get yourself a multimeter.

Download and print this section of the tsrm.

Follow the diagnostic steps in the tsrm.

 

[supraman7mgte]

Hmmm,I always thought that the alternator supplies voltage to the electrical AND the battery.
Sounds like you might have a bad diode in the alternator,have you pulled it abd had it checked?

 

[barkz]

bump? lol

 

[hvyman]

Alt supplies the car with the voltage it needs to stay running while continuously charging the battery. Battery is only there for start up. When the alt dies your car will use the battery and then shut off after about 15-30min when the battery is done.

 

[xdreamkustoms]

Check the three wires near the intake. I think they are red, black and yellow. the plug that clips into the back of the alt has the same color wires. I had the same problem with mine, even though its a 1JZ swap. I bought a new alt, fuses, and re-wired the main post. It ended up being the three wires pulled loose from the connector. Hope that helps.

 

[Heavy D]

i put a new alt as well, theres time that my alt be saying 12.9 and even times it will go to 11 but the battery light will not turn on, and times it will be at 14.4 and stay most of the time at 14.1, and the alt is brand new from the store, my last alt was junk and i was on the high way forcing my self back home at 8volts going at 100mph to make it home so it wouldnt die on the highway

 

[bioskyline]

the 3 prong plug is to excite the coil inside the alt and run the regulator. the alt needs power before i can make power. so check the plug and the wires.

 

[hvyman]

You can get bad new alts. Had it happen a couple times at work.

 

[D.J.T.]

Back in the day my old man would just buy the brushes & replaced them & viola! fixed alternator. :] Im not Alternator expert though..

 

[hvyman]

Ya ive done that before too. Iirc you can also still get the regulator from Toyota separate from the alt same with brushes. Iirc brushes were like 12 bux with discount.

 

[modmonster2008]

Alternator voltage regulator and generator brushes can still be replaced, done it on my car

 

[Nick M]

Hmmm,I always thought that the alternator supplies voltage to the electrical AND the battery.

It does. The positive side is parallel up to circuit protection.

Alternator voltage regulator and generator brushes can still be replaced, done it on my car

Yep. And they are cheaper even from Toyota than getting a new one. Toyota gets about $600 on a new one.

A reman from Toyota is a bit up in the air. Toyota changed the part number on the recitifier and price from $129, to $400. Why, I don't know. Even Nippondenso is manufacturing in China now. If you can get a low price reman from Toyota, that is the best deal. It will have new brushes, bearings, and probably rectifier and regulator.

Of course, if your cables are green and white instead of copper color, that is why you are not getting a charge.