• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Duramax Alternator

RI Chevy Silveradoman

RI Chevy Silveradoman

At your service
Staff member
Lead Moderator
Messages
16,722
Reaction score
15,536
Location
Rhode Island
I was having issues with batteries being dead. I fully charged both batteries and truck was fine. After running the truck, then letting it sit overnight, no start the next morning. I fully charged batteries again and got truck fired up. I put volt meter on battery and got 13 volts. Lat time I checked I was getting around 14.7 volts. Belt is good. Alternator is original.
I spoke to someone who was telling me there are 2 charging circuits for GM, low speed and high speed charging based on engine RPMs. Has anyone heard or know about this? Anything else I should check before getting a new alternator?
 
Last edited:
No 2 speed alternator I ever heard of. But every other one basically doesn’t start putting out until a certain rpm, then puts out more the faster it spins. That pretty much how all alternators work.
There is a circuit that “reads” battery power and will work like an on/off switch. When the batteries are full & no major electrical draw is present the alternator will stop putting out. When the draw is present wether headlights, battery, etc then it will begin putting out power again. Magic pixies.

Stop by most any autoparts store and have them come out and hook up a tester on the alternator. Around here they all do it for free in hopes you buy the new one from them. There is YouTube videos how they do the test so you can see whag to watch for to ma sure they don’t lie about it being bad.
 
GM trucks with Regulated Voltage Control (RVC) alternator systems include models from 2007 onwards, particularly the half-ton trucks and heavy-duty models like the Silverado and Sierra. This system is designed to optimize battery life and improve fuel economy by managing the charging voltage.
 
Hmm so wonder if I have one on my 2013 tahoe ppv.
Some of you know since i cant physically do mechanics anymore i went back to being an electrician. Funny thing about alternators & lead acid batteries- the faster you charge them the faster they charge up to 80% no matter what. And alternator life is a joke if they try to improve because the stock ones outlast the warranty by 4 fold.

Running an alternator to charge up 100 amp hours- if it is at 10 amps charging, it takes 10 hours. If at 50 amps charging it takes 2 hours. And 100 amps charging it takes 1 hour. It is linear.
If you charge it to fast it will shorten the life on the battery. But battery life of 3/36 usually makes it without failures through warranty. I am surprised they chased it T all because better battery tech exists if they wanted that.

The efficiency is directly proportional to the power savings potential. 745.7 watts equals 1hp now multiply by the efficiency number and there you get your electrical energy.

Alternators are built the same as AC motors. The style brushes, windings, etc used in the older ones like the ad44 is 93% efficiency. Meaning 7% of the mechanical energy to spin it does not go i to the battery. Until you go brushless you can not get any motor or alternator to 95%. The most advanced units in the world that cost tens of thousands of dollars is 98.5%- uses gold connectors, ac refrigerators to keep them cool, super conductors… so how much can they really help it…? Puzzling. Oh-that award winning insane great motor that Telsa stuffs in their cars which are unsurpassed still- 97%. See, the efficiency has to improve. Batteries actually last the longest if you charge up to 80% for lithium ion & 82% for lead acid. Then stop.
A simple voltage monitor and controlling it to stop makes the average lead acid life go from 39 months to 43 months according to the best solar battery engineers- and they are the top of the food chain currently. But that includes somewhat controlled temperatures.

If they made the new alt so it is say 96% efficiency and costs under $4,000- that is the comparison of a 800’torque/400 hp truck getting 120mpg.


That has my gears turning and wrecked my sleep tonight- haha.

The math just aint mathing.

I wonder if it’s something like gubmint grant money for chasing the rabbit like what happened with electric cars.

Here’s an example for ya- drive your rig 200 miles and measure mpg with and without the A/C on full. We know the impact there. Call it a loss of 3 MPG THEN JUMP OFF A BRIDGE BECAUSE 3 is insane! Haha.

I and many rv folks look into running a 120vac hvac off the engine alternator. My ad244 - it needs 3 to handle it. Actually a hair more but i was willing to add 3 and let it drain my battery because they are oversized batteries. So roughly figure how much mpg do you loose running your a/c. Now divide by 3 to equal your alternator. Thats the 93% efficient one. You need to figure maybe 3% at best - and that is seriously pushing close to motors and alternators that only exist in labratories or the motors that tesla wont release the patens on. And remember GM is getting murdered in ev wlrld because of their motors and batteries can’t compete with tesla.

Now do the math of one alternator is 1 mpg. What is 3% =0.03 mpg

If you have a 25 mpg truck and add that wazoo unit- congratulations you now get
25.03 mpg. You extended the battery life as much as if you just put in a battery that is 15% larger in size and kept the old alternator.

Maybe something like dexcool and dexron3 where patents expired and all the simple designs are beyond patents also?

Maybe I am not seeing the forest for the trees.
But remember many years ago was all the talk of all cars would soon be 48 volt electrical systems even in gasoline cars to spool up electric turbos and I laughed it off and said it doesn’t add up? Said the technology doesn’t exist to get us close?
I will risk the crow pie & say it here too.

Disconnect your alternator wire & tape it up so it doesn’t short out & drive 100 miles measuring mpg. The plug it in to charge the now low battery, turn on headlights, spotlights, big stereo. & drive again. The mpg difference and divide by. 9 for 90% efficiency.
Its just insane.
 
I couldn’t resist it. I remember mythbusters did the test of mpg on ac vs windows down. Running what appears like a 2000ish model explorer- the computer showed running the ac used 0.1 mpg
Windows down showed using 0.5 mpg

They finished the test by comparing an explorer vs a suburban and the explorer ran out of gas first the suburban had windows down and explorer had ac on- but thats just suburban getting better mpg than explorer so later when revisited in the show they acknowledged that was a mistake and said the numbers were reproved that ac on with windows up is better mpg than ac off and windows down, especially over 55mph.

But the key here is older explorer burned 0.1 mpg for the ac. Now figure the mpg to save even as high as 5% of one alternator.

Its nuts.
 
Well. I changed out the new alternator and new serpentine belt. It charges now. I went to buy new batteries, and they only had 1 in stock. WTF.
So hopefully next week all should be good. 👍
Very odd, my fluke initially gave me only 13v last week when I started having the issue. Judt before diagnosing that the alternator may be tired, the fluke would not give me a steady reading at all. It constantly jumped around and gave crazy readings. I confirmed that with a Klien multimeter. The meter on the dash was reading pretty low compared to the normal reading for my truck of just over 14 mark.
I bought a new 220A alternator from XDP. Was just a tick more than a rebuilt around here. Time will tell here how this lasts. But the 145A alternator was OEM to the truck, 2006, so I guess I got my money's worth. Just a tick over 200k on the odometer. I grew up with my pop doing all the rebuilding himself. We used to go to a small store and buy the new innerds and rebuild it. Bearing, voltage regulator etc. He even used to experiment and overwind the motors a bit to get more juice. I looked, those stores seem to be all gone now. 🤷‍♂️. AND I read some reviews on some big store alternator rebuilds, and they were abysmal at best. Thus my choice of going new. Someone told me it would be a waste going to 220A from 145A on a diesel truck, but I just couldn't resist. When I started it yesterday, headlights were definitely brighter, as well as cab lights and interior lights.
 
Glad you are dialed in Over 200k is good life.
Do they have the 2nd battery on order for you? Running mismatch isn’t great but for a week or so won’t kill the new one.

For diy alternator rebuilds- True Value Hardware stores usually sell individual brushes, bearings, etc. How well they can look up your type if not a normal stocked part is luck on how good is the employee you have- not to be biased but if ya have an old guy, like a Bob or Frank, you usually have a chance. When it is Tristen or Skyler, ya might not fair so well.


Back into “Will went off the deep end again”:
On the new wazoo designed alternator - one of the biggest efficiency improvements is to be brushless. Yeah- I woke up after 3hr & 20 minutes of sleep and it’s in my mind still. I probably should seek a mental health professional about my OCD again- it sneaks up on me at times. Haha.
Brushless and ceramic coated bearings could bump efficiency enough to be worth it in mass production. The regulator pulling in two stages is just a step innthe opposite direction rather than variable amperage which would keep the voltage the same yet allow it to charge say 75 amps at 1500rpm, then 100 amps at 1750, 125 amps at 2,000 rpm, etc. but could be set up for about any rate of climb kind of like a pwm in reverse. But it would not have to always vary the amperage based on rpmIt’s really a lot more in the efficiency category.

Doing it in two stages instead of progressively is cheaper done by two set of resistors and can control the two charging rates far more accurately - but use of resistors quickly thrashes into the efficiency of it. Like saying- I want the highest mpg so I dont have to fill up with fuel once a week-so you spend thousands into mpg improvements on the truck, but then you tow a 8,000 pound camp trailer everywhere you go so that when you do have to fuel up you can use your own bathroom- since thats why you don’t like stopping. Its just painfully counter productive.

Oh- & I was wrong- They had two fords in the test. That bothered me thinking they would do that- they didn’t. Idk why ai thought the white one was a chev when i saw that. It was just two different fords instead or running one truck two times. That was still an invalid test imo. Too many variables. Should have been one truck. With a truck getting under 12mpg - it wouldn’t have been too long a test. SMH.
 
You must log in or register to reply here.
Back
Top