99 Suburban Charging/Low Idle Frustrations

[android]

So I have started having a problem with my 99 burb charging. Being as it is coming up on summer I have been running the snot out of my A/C. My dash volt meter has been wonky for a while so I got a Stinger one that I trust. It charges around 14 all the time, it even does alright when you turn all the fans on high, charging around 13.5. If you turn the headlights on it still does alright, around 13.3. It is only when you put it in gear that it pretty much looses the plot, around 12.5. My hot in gear idle according to my laptop is around 515rpm. Hot idle in park is 600-650 and it does alright.

The truck has a 140 amp alternator which is good and even new. New battery which is top post, which I used the clamp style connections on and simply cut the side posts off and stripped the wires back. So today being Sunday 5/8 I went all out overkill and replaced the leads from the battery to the main fuse, from the alternator to the main fuse and from the main fuse clean across the truck to the fuse box with 2 gauge wire. I put proper ring terminals on and WOW even heat shrinked them. I cleaned all the connections I could easily get to and put ring terminals on the ground wire and positive to the starter. This has a very positive effect on the situation, my volt gauge in the dash reads correctly. The voltage is higher now, the lights a brighter, windshield wipers go like hell, windows go up and down faster, crap even the interior lights are bright. BUUUUTTTT it still has the same problem when it comes off cold idle and gets up to temp, I can turn everything on high and it struggles to achieve 13V in gear.

If you raise the rpm in gear just 100rpm to get it to 600ish it charges full at 13.8 even with everything running. I have had a problem with the truck stalling at idle, so I cleaned the throttle body VERY WELL. Made minimal difference in idle speed, but fixed the stalling. I am at the end of my rope with this one. I have several things which I know or have been told will fix this, mainly hoping for some 3rd party feedback. The IAC seems to work fine, now that is clean. Maybe pull the intake and sandblast all the carbon off. I haven't looked at fuel trims to point towards a lazy o2 sensor, there very original with 215k. I applaud any who read this whole thing, I know there are a lot of variables in this some which may or may not directly deal with charging, any input is appreciated.

 

[redfishsc]

Same thing happening to me, 1999 Suburban (2WD) with the 140 amp alternator. Did you get yours from Autozone, sometime around December last year, lol?

I didn't make any specific upgrades to anything when I did it, I just bolted it on and put on the bigger drive belt.

I'm using an OBD2 app on an Android phone (Torque Pro) to read real-time measurements, and did a 600 mile round trip, towing a small camper this weekend. The app can also give live trans temp readings, which was neat.

Using that app, with the phone sitting up on the dashboard using BIG readouts, voltage varied from 12.7 to 13.7, usually about 13.3, but it never stayed in one spot for more than a few seconds.

Anyway, my suspicion in my case is that I'm going to be swapping this alt soon. I had the guys at Autozone check it with their scanner, and said that it was reading lower than he'd expect (down to 13.1, bouncing up and down). Funny thing was, it said that my battery failed, voltage was 12.67. Haven't had any battery problems, it's an Interstate battery with full water and should still have several good years service.