Ok, im a little foggy on the voltages that are supposed to be on what wire. Im having issues with the rear battery not charging and the Gen 2 light is on. I know there is an exciter wire for each altenator. I also know that one of the wires in the plug recieves voltage all the time and the other when the ignition is on. Right? When I meter out the wires on the plugs, what should I be reading for the red wire driver's and passenger side, and the brown wire driver's and passenger side? Should there be 12v to the driver's side and 24v to the passenger side exciter wires? Im pulling my hair out here! Thanks!
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Voltages
- Thread starter bpcole
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Barrman
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The passenger side alternator charges the rear battery. That is ALT 2.
With the plug on the alternator un plugged. You should have 12 volts on the red wire with the key on or off. The brown wire should be 0 with the key off and 12 volts with the key on. If you are getting that, the problem is inside your alternator.
All measurements are with the ground of your volt meter on the rear battery negative terminal. If you just put it to ground, all readings will be in the 24V scale.
With the plug on the alternator un plugged. You should have 12 volts on the red wire with the key on or off. The brown wire should be 0 with the key off and 12 volts with the key on. If you are getting that, the problem is inside your alternator.
All measurements are with the ground of your volt meter on the rear battery negative terminal. If you just put it to ground, all readings will be in the 24V scale.
Just to clarify what Barrman said.
If you ground your meter to the rear battery negative post then you will have 12v readings for GEN2.
If you ground to the truck then you will have 24v readings for GEN2.
Red wire will be hot all the time and the brown wire will be hot only when the key is in the RUN position.
The GEN1 will have 12v readings using the front battery ground or the chassis ground.
If you ground your meter to the rear battery negative post then you will have 12v readings for GEN2.
If you ground to the truck then you will have 24v readings for GEN2.
Red wire will be hot all the time and the brown wire will be hot only when the key is in the RUN position.
The GEN1 will have 12v readings using the front battery ground or the chassis ground.
Ok, thanks for the info. Just got done checking the exciter wire and the other wire in the plugs on top of both the altenators. They checked out just like y'all said. 12v constant to the red wire, and 12v when keyed on for the brown wire. That goes for both sides. I also cleaned up terminals and replaced ones I thought needed replacing. The Gen 2 light is still on, however. I had the altenator checked at AdvancedAuto when the light first came on and it checked out fine. What next?!?!
Barrman
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What are you getting for voltages at each battery with the truck running and everything hooked up?
Is the red wire at the bolt post on the back of ALT 2 always hot with 12V?
It seems to me that your truck wiring is ok. That means no matter what autozone said, you have a problem in your alternator. Is the belt tight? I would suggest pulling the alternator and checking the diode, regulator and rectifier with a DVOM as per the -34. Something is either bad or a connection is loose.
Is the red wire at the bolt post on the back of ALT 2 always hot with 12V?
It seems to me that your truck wiring is ok. That means no matter what autozone said, you have a problem in your alternator. Is the belt tight? I would suggest pulling the alternator and checking the diode, regulator and rectifier with a DVOM as per the -34. Something is either bad or a connection is loose.
Ok here's the update, took off both altenators. Replaced the loose belt. Put Gen 1 in the place of Gen 2. Put a new altenator I had in the barn in the Gen 1 position. Wired everything back up. No Gen lights now and 14.2v to the back battery and 12.7v to the front battery. The volt meter is halfway into the green. We will see what happens in the coming days. Thanks for the help guys.
Barrman
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14.4 is what you should have at each battery. Something seems to be bad with that one alt.
Truck is still cranking fine, no Gen lights, but my speedometer and gas gauge backlights are not working now! Everything else in the instrument cluster is backlit (ie the wait light, fan switches, Gen lights, volt meter), just the gas gauge and the speedometer. Any ideas?
southdave
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Ground off the drivers side alt, that what fixed mine
Barrman
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The back light for the gauges are a completly different problem. Except for 1 wire. The ground for the dash lights and about 20 other things on the truck is bolted to the top of the parking brake pedal bracket. Crawl under there, remove the bolt, clean the metal and make sure that ground is tight and making contact.