2009 GMC Envoy low voltage

Any slight flickering on headlights or internal lights when driving? I feel your pain, I went through 4 alts.

I had flickering of head lights and internal lights. Changing the alternator fixed that problem, but now I'm on alternator#3 and have the low voltage issue.

My 2008 Envoy is doing the exact same thing (14+ at start, 10min later=13.0, restart=14+ again, repeat) . . Mine is also intermittently (once a week, or so) draining the batt w/key off, to the point of reading (hand-held meter) around 5.0volts, after only 2 hours of key off (doors closed, no sounds, no lights) . . The trouble I'm having with trying to locate the source of the drain is that the condition corrects itself (stops draining) before I can find anything, once I jump it or recharge the batt . . It did act up again last night (went to get in the car, inter lights dim), so I attached a volt meter, batt at around 5.0v, so, at the front fuse box, I started pulling fuses, circuit breakers, and didn't find anything substantial, went to the rear fuse box (opened the driver side rear door, and waited for the inter lights to cycle off) and did the same . . There, I found that removing the RADIO fuse (#41) would stop the continuing drop in voltage, and the meter would then start climbing, to around 8.0v, after 3 or 4 minutes of no radio fuse . . Removing the fuse (#27) for On-Star, produced similar results . . I was careful NOT to turn the key on, or open / close a door, etc, while doing all this, trying to avoid any "jog" or "jolt" to the system, which might "reset" whatever is causing the problem, and losing the active draining condition . . After removing the 2 fuses, and once the voltage had stabilized at around 8.0v (and with the Radio and On-Star fuses still removed), I disconnected the lead from the batt to front fuse box (killing both boxes), and tested the batt . . I only saw a voltage increase of about 0.02v (very acceptable) . . With that lead still disconnected, I then disconnected the batt, and tested for voltage there, just to see if there was any change, in an attempt to eliminate the starter and alternator (the only 2 items directly connected to the battery, and could be draining independently of anything in either fuse box) . . There was no change at all from this test . . I realize that doing all these tests while the batt was well below normal voltage, the changes that I was seeing could be due to that low voltage (these changes would be seen, when dealing with a battery as such a low voltage, even if there was no legitimate drain condition happening at that time . . that is, another Envoy, with NO drain condition, would have produced the same test results, if the battery was that low when doing the same tests . . So, I reconnected the batt and fuse box lead, left the 2 fuses out, and 2amp trickle charged the batt for an hour or so . . Disc'd charger, let the batt stabilize, got a steady 12.5 volts . . With the doors still open (never closed them, and still never even put the key into ign switch), and the handheld voltmeter still attached, I re-installed the Radio fuse . . This caused the "door open and key in the ign" chime to sound for a couple of seconds (nothing happening at the radio itself, I watched for that), and the voltage did drop by about 0.2 volts, but only for 3 or 4 seconds, then it crept back up, to within 0.02 of what I had, before re-installing the fuse . . I left that fuse in, and then re-installed the On-Star fuse, and got no change . . For now, I'm leaving the fuses in, and waiting for the thing to screw up again, and (hopefully, I'll catch it in the act, and before the batt goes down too far for reliable testing) try again, to find a source of the drain . . I'm guessing that any one of the disconnects, fuse pulls, etc., which I was doing, could have caused the active draining condition to "reset" (or otherwise correct itself), and so, the test results that I was seeing were actually incorrect, but they're all I have to go by, at this point . . 'm still wondering if the "13volts at idle, about 10 minutes after start" deal, is somehow related to the rapid draining deal . . Once the 13volts deal happens, the voltage doesn't change (more than half a volt or so), even with higher rpm's, turning accys on or off, etc. . . I've verified the dash gage reading, against a handheld meter, and the gage is reading properly . . That 13.0volts won't change until the key is turned off, and the engine is restarted, the same as the other vehicle mentioned in the previous message . . So, any thoughts? . . My guess is that it's going to take finding someone who has had the exact same problem (the rapid draining issue, anyway), to finally find an answer . . Until then, Thanks So Much for listening! . . Chuck.