DR44G GMC alternator

Geo-TH,In · Jan 5, 2012

I bought my 2007 GMC truck new. It now has 42,000 miles. Was told by the dealer my battery has a full charge and failed the load test. I can charge up the battery, let is sit for 24 hours. It produces 13.2 volts and 11.2 volts under a 100 amp load test. Bought a new battery. Charged it up because I didn't know how long the battery had sit on the store shelf. It too produces the same results 24 hours after removing the charger, 13.2 v and 11.2 v under load.

Been watching the voltmeter on the dash. About 1/2 way home, the truck's voltmeter drops to 12.5 volts. By the time I get home, sure enough the battery's voltage is 12.5v and it fails the load test.

I installed a new battery tonight. I think there is something wrong with the alternator or the voltage regulator. All the wires look like they did when the truck was new. No oxidation on any thing. Belt has no cracks and doesn't squeak. The dr44g gmc alternator is a 240 amp alternator and it's expensive. If the problem continues I'll replace voltage regulator.

Has anyone experienced a similar problem with the 240 amp alternator?
George

Michael Soldan · Jan 5, 2012

A 12 volt alternator needs to produce 13.0 to 14 volts in order to charge a 12 volt system,when I test an alternator and its anywhere less than 13 its toast,time to rebuild them.We have a guy close to us who is a whiz at rebuilding them,usually a $25 to 35 job and they work..quick and cheap!

Geo-TH,In · Jan 5, 2012

Michael, The alternator does produce 14.5 volts. Half way home it stops working at the same location the past few nights. So how can it work 1/2 the time if it is toast?
George

J.Wondergem · Jan 5, 2012

I had one, that would charge sometimes and not other. Turned out, the brushes were wore down and would only make a connection intermittently.

Anonymous-0 · Jan 5, 2012

Had a 97 GMC was acting the same way it was a voltsage regulator. The regulator on this alternator was bolted on the back of the alternator.

Janicholson · Jan 5, 2012

A heat affected regulator, or a rectifier going out when it gets warmed up will do it. It should stay at 14.2 or a little more, all the time. I would start by giving at a magnetism test when it is not putting out. When first started, the end (away from the pulley) will be magneticuse a hacksaw blade or other tool to feel the magnetic attraction of the bearing/shaft. When it quits charging see if the same magnetism is there. If not I would replace the regulator, if yes, I would think it is in the stator windings, or Power Diodes. Jim

RusselAZ · Jan 5, 2012

It is not a problem, that is operating as designed. Your battery is not failing load test.

When the voltage goes to 12 volt,(it can go as low as 11 in normal operation) the system is in a fuel saver mode. When it goes to 12 volt if you put the transmission in tow range it will resume showing around 14 volts. turning the headlights on will also bring the voltage up.

When the alternator is replaced it has to be programmed to the vehicles computers.

Sprint 6 · Jan 6, 2012

Your alternator and volt meter are working fine. That system has a sensor around the ground cable near the battery. It uses that current sensor to sense electrical load and state of charge. GM did that to help save batteries, continually charging a battery at 14.5 volts will boil the battery. The system is designed to keep the battery at near 12 volts unless there is a high electrical demand. If you replace the alternator, the new one will do the same thing. I would charge the battery with a charger, start the truck once to pull off the surface charge, then do a normal load test.

Geo-TH,In · Jan 6, 2012

Russel, You are the recipient of Yesterday Tractor Gold Metal Award, YTGMA for saving me from buying a new alternator. On the way in to town this morning the alternator kept the voltmeter at 14.5v, where it stays all the time. It was dark and the lights were on, keeping the alternator active. Thank you very much for your advice.

Later today, I'll be going home before it gets dark. It wouldn't surprise me that after I go past the last stop light in town, I may find the alternator taking a nap, like it has done in the past. If it does ,I'll turn the head lights on, heater fan, wipers and shifting in to the towing.

Dealer said about 3000 miles ago, I needed a new battery, which I installed last night after charging it.

Thanks again. Your award just gives you bragging rights for finding my problem.

George

RusselAZ · Jan 6, 2012

"Blush"

Out here we expect 3 years from a battery. Putting a new battery in after five is just a good idea.

I'm afraid there will be lots of frustration in the future about these newer charging systems. All the manufacturers are doing it as they use every trick to get better mileage. The vehicle will tell you it needs a battery long before it is dead. The system is being checked every time the key goes from off to on or at idle.

There is about a page and half of things these new systems do. You're welcome.

Geo-TH,In · Jan 6, 2012

Russel,

Thanks again. On the way home, I kept an eye on the truck's voltmeter. I had to stop off twice before heading home. The truck's voltmeter was between 14.5 and 15v. Made it past the last stop light and everything was fine. 4 miles from home, the battery must have been happy and the alternator voltage dropped to 14 v. 2 miles from home, the voltage dropped to 13.5. Turned everything on and voltage returned to 14. I'm happy it only cost me a battery, which I bought about 4 weeks ago from Rural King for $45 on sale. Going to keep the truck battery. I'm sure my old tractors will be happy with it.

The rest of you who responded get GOLD STARS

Thanks to all,
George

Anonymous-0 · Jan 6, 2012

So..... at what point do you shove this info up that dealer's as$??? Sounds like he was trying to take an old guy for a ride..... Or did I misread something?

Geo-TH,In · Jan 6, 2012

Dave, My dealer told me I had a battery that had a full charge, but it failed the load test. This was about 3000 miles ago. I tried to bring the battery around with different charging techniques and load testing. The battery seemed to be working just fine. Truck started, seemed like there were no problems. Then the alternator started acting up, it would stop charging about half way home, draining the battery. That's when I decided to put the new battery in. I had purchased over the battery a month ago after finding it on sale for $45. That seemed to solve my problem.

Now Dave, I need to work on my people skills before I tell anyone to stick it

That said, the dealer wanted $165 to install a new delco battery. Autozone wanted $95 and I got a cheap excide from Rural King for $45. It was on sale at the time. Glad I bought it when I did.

Sorry for all the confusion.

George

DR44G GMC alternator

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