gowic

im trying to fix a 2008 gmc 2500hd duramax at the moment and am starting to get stumped. I kno that it's normal for the charge indicator not to come up for the first minute or so while the glow plugs and intake heater are drawing current. But this morning i timed it and it took about 8 minutes before the indicator would come up to 14v it even gets to the point where the lights start to dim down. The alternator has been replaced and the problem still persists. does anybody have any insight into this problem?

AUTOT3K

iTrader: (3)

Check for voltage drops over all your primary connections. Battery positive to positive cable end.battery poitive to alternator positive. Battery ground to negative cable end. Alternator ground to battery ground. Do it under load and you shouldn't see more then a 0.5V drop otherwise you've got a poor connection or broken wires or resistance from something.
Also....was the new alternator tested? I know it's new but try an Avr anyways and see what the alternator is really doing

gowic

yes, i did have the alternator on the avr and it was working fine.... all the connections are clean and tight.. and after the vehicle has been warmed up for around 10 mins everything works great...

AUTOT3K

iTrader: (3)

Im not to familiar with the duramax charging system but is the voltage regulator inside the alternator or is it controlled by the BCM?
another easy test to do with your DVOM is an actual voltage regulator test where you test from the alternator positive to the case ground and with the accessories loaded you should see AT minimum I think....12.6V i'd double check that number though and it should fluctuate a bit as it attempts to get to 14v.
I guess the issue your having is its gotta be cold and as your testing...its warming up! then you gotta let it sit for a while to cool back down

AUTOT3K

iTrader: (3)

which avr machine are you using? is it an automatic one just push a button and walk away or is it the nice carbon pile one you can control the load?

AKlowriderZ71

iTrader: (22)

I haven't timed it, but my Duramax takes a minute or two before the volt gauge jumps up to 14 volts also. At the same time, the lights are dimmer than normal, and the heater blower motor is spinning slower. Then the gauge pops up, the lights get bright, and the blower gets stronger. I've never worried about it or tried to troubleshoot it, as every Duramax I've cold started does the exact same thing.

gowic

it's a snap-on avr with a carbon pile

i understand that its normal in the first couple mintues, but this goes on for nearly 10 minute and its only been doing it in the past 5 days



I think I'll try to check and see if something is causing the glow plugs to stay on for an extended period of time, or other things drawing current that shouldn't be. Apparently this vehicle has been plagued with electrical problems since new.

gowic

well problem is solved! turns out the owner had slightly exaggerated how the long problem was occuring for... the 10 minute no charge period magically became about 3 minutes with further investigation... so basically nothing is wrong thanks everyone for ur input

TIM Z

iTrader: (12)

Lol , mine does the same thing . Just a dmax thing I guess .

stock48

iTrader: (16)

Same here. It's the grid heater in intake, combined with glow plugs. Thing is like 1500 watts.. I have seen issue with alternator charge wire where it connects inside the little red junction box.