Help needed with 99 Diesel Suburban alternator or battery? [Expired Topic]

[conurema3]

Hi all,
We got in our new (bought in July with 147K mi) 99 K2500 diesel suburban this morning (last night temp was about 38 deg F) and we noticed the windows were moving quite slowly, then we noticed that the radio got all distorted, looked at the battery charge gauge and noticed that it had fallen to close to 9 volts, usual charge being close to 14 volts. We immediately drove (in first gear in the automatic, mind you) to town 25mins or so away to see what was wrong. Talked to our regular mechanic on phone in a different state, and he explained if there was an electrical problem going on (i.e. alternator or something else) that it wouldn't shift due to the transmission being dependent on the electrical system. : ) So we go to local chevy dealer in new town, we don't know, they run all kinds of electrical system tests, miraculously the suburban starts holding charge again and they figure out that we have a faulty alternator and a battery with bad fuel cell. They replace secondary batt and alternator to the tune of $580-. We drive home and notice charge is only 12v. Eveything works, so we figure its okay. We just went out to run errand again, and charge has now dropped to only 10.5 volts? or less? any idea? This is our first diesel vehicle and we have no idea what's going on... any suggestions? we are supposed to be driving the 'burb 3hrs tomorrow and are worried about whether it will make it... thanks!! everything was going great until this...

[Steve]

Welcome to the site. I'll have to defer to one of the diesle guys.

[unplugged]

I'd loosen the positive battery terminal and start the engine. After it has started disconnect the battery. If it stays running the alternator is putting out enough current to keep up with the load in the vehicle. A car runs off the alternator, not the battery. The battery is the reserve that is used for starting and for limited accessory use when the engine isn't running. If the engine quits, then the alternator isn't up to the job. Get it replaced under the warranty. If you are worried about the battery, any parts store will load test it for little or nothing.

One other thing. Check the engine block to chasiss ground cables. There will be at least two per side usually. I have seen weired electrical bugs caused by lack of engine block to chasiss grounding.