Alternator Question??

[John R]

I've have another question, the volt gage in my truck stays down like it's not charging when I first start it in the morning, and it stays this way until I get going down the road then it jumps up to normal and is good for that drive.

When I shut off the truck and come back to it, the same thing happens all over again.

Is this normal, or do I have A problem starting to show up?

[Shaners]

I'd talk to the service guys about that.... I don't think it is "normal". Mine is always showing 14 volts or more!!!

[GF7PE]

could be as simple as a bada belt. For the $10 change it. Then if it still does it, it may be an alternator or volt reg prob (same part)

[hosspuller]

Sounds like the alternater isn't getting enough speed to begin self-excitation ( sounds immoral) and charging.

 

Test it by reving the engine after start-up. if after the run up the voltage is normal, start checking the alternater, check the drive belt(s) and the motor idle speed.

[LARSONEM]

It has nothing to do with the alternator not spinning fast enough or a slipping belt. It has something to do with your diesel engine and the glow plug system. Mine Duramax does the same thing, although it's more of a momentary thing. By the time I get the truck backed out of the garage and turned around to head out of the driveway, it's usually showing a good charge.

 

Remember that the diesel is a compression ignition engine, based upon heat as opposed to a gas engine being a spark based ignition. The purpose of the glow plug system is to heat the air in the cylinder so when the fuel is injected and compressed it ignites. In a cold diesel engine, the glow plug system must remain engaged for a short duration of time to heat the air in the cylinders until enough compression ignition cycles have occurred to automatically to keep the engine running (warmed cylinders).

 

I had an Oldsmobile diesel in the 80's and you could constantly hear the relay for the glow plug system turning on and off when the engine was cold. Each time it went on and off, you would see the voltmeter drop way low (my Cutlass had the optional rally cluster gauges as opposed to idiot lights).

 

In answer to your question, my guess is that the glow plug system on the Duramax stays engaged for a very short period of time and this is what is causing your problems. If the "wait to start" light doesn't iluminate, you probably won't see any difference in the volt meter, as the glow plug system isn't energizing.

 

Eric

2003 Silverado HD CC D/A