still confused with the alternators

[travis8352]

my trucks wiring is stock and it is still 24v. when i turn the key, power on, engine is off. both gen 1 and gen 2 lights are on. engine starts my gen 1 and gen 2 lights are still on. i rev the engine and the gen 2 light turns off but gen 1 stays on. as soon as i let off the gen 2 light is back on. whats my problem?

 

[cucvrus]

Do you have a volt meter?

 

[Tinstar]

A Digital multimeter is required equipment if you own a CUCV.

 

[travis8352]

Do you have a volt meter?

yes i do. when i revved it and the lights turned off the battery was at 14. something volts. i had my brother checking voltage while i revved it so im not sure on the exact voltage. but while i was typing this post i went out to check on the truck as i had left it idling the gen 2 light was off at idle and the battery voltage was about 14.8 volts i believe. the front battery was at 12.09 volts after idling for about 20 minutes or so. when i first fired it up the front battery was at 12.15 volts. the gen 1 alternator charges the front battery correct?

 

[scottladdy]

the gen 1 alternator charges the front battery correct?

Correct. It is the left or drivers side alternator.

Are your accessory drive belts properly tensioned?

What is the voltage when the engine is revved a bit for each battery?

 

[richingalveston]

first disconnect and test each battery, a dead cell can cause problems.

I would bet however you need alt 1 rebuilt and alt 2 is not far behind from needing a rebuild.

 

[ken]

Try removing the ground to the front battery while the truck is running. Does the engine die? If not, what is the voltage at the alternators positive terminal? I with Rich though. I think alt rebuilds are in your future.

 

[travis8352]

Correct. It is the left or drivers side alternator.

Are your accessory drive belts properly tensioned?

What is the voltage when the engine is revved a bit for each battery?

when i revved it yesterday the voltage at the rear battery was over 14 volts. i wasnt the one checking the voltage so i dont know the exact voltage but it was over 14. the front battery was at 12.12

 

[travis8352]

batteries should be fine they are brand new. i know i will need to rebuild atleast alt 1 im just trying to gain more knowledge on these alternators. ive been researching but i keep confusing myself

 

[travis8352]

i will try that when i fire it up today. i know i will need to rebuild alt 1 im just wondering if what im experiencing is normal for gen 2

 

[richingalveston]

It is somewhat a simple system.
Atl1 (drivers side) outputs 12V to the 12V bus on firewall (next to brake booster) and it also outputs to the input of alt 2. Just like your front battery is connected to the back battery and also to the 12 volt bus.

The battery cables can be confusing since the out put is actually on the + of the back battery but at that point the voltage is still 12volt since it has not passed through the back battery yet..

The passenger side alt is the 24 it acts just like your back battery. it takes in 12volt and outputs 24 volt. This output is the large bus bar on the passenger side.
Go ahead and get alt one fixed, pull it bench test it and then I recommend rebuilding it, the kit is cheap and they are easy to do no special tools.

running it the way it is, is a sure way to mess up alt 2 if it is not already. You may want to post pics of your alts to confirm they are stock. both should be the same isolated ground. Both take the same kit so I would by two and do them both and then be happy.

Once it is fixed, you can then take the meter and get to understand it better.

The front battery gets charged through the 12volt bus when the engine is running, the back battery gets charged through the output of the second alternator.

Hope it helps.
rich

 

[MarcusOReallyus]

i will try that when i fire it up today. i know i will need to rebuild alt 1 im just wondering if what im experiencing is normal for gen 2

Think if your batteries as flashlight batteries. They are "stacked" on top of each other, electrically, like a flashlight sitting upright on its tail. The + of the front battery goes to the - of the rear battery, just like in a flashlight, the nose (+) of the bottom battery sits against the tail (-) of the upper battery, and their voltages ADD together.

The two alternators are connected to the two batteries; + of alt to + of battery, - of alt to - of battery, in each case. The ONLY difference is, one of those alts makes its - connection through the chassis (what we usually call GROUND), and one of them makes its - connection through some wires that do NOT touch ground.

What gets people all wound up is the question of GROUND. People have the idea that GROUND is some magical, mystical absolute point. It's not. If we never electrically connected ANYTHING in a vehicle to the chassis, nobody would be confused by this system. We'd have two wires running to every light, gauge, blower motor, anything electrical, and the circuits would be easy to trace. The + and the - of each ALT would be wired to the + and the - of each battery, and everything would make sense to everybody.



We'd also spend a lot more money on wire in a vehicle, and we'd have more crowded wire looms. Which is why we borrow the convenient electrically conductive body of the vehicle to run the other side of the circuit, and we call that "GROUND", and everybody gets confused.