Low Voltage & Batt Light on with NEW Battery

Maintenance/Repairs
1

1999 Suburban (gas) stopped mid-intersection and only ran briefly off jumper cables. No lights or apparent electrical activity. Towed and and replaced battery. Ground cable had worked loose recently with intermittent starting problems that resolved after tightening. Arcing was evident on ground cable after replacement. Hood light came on immediately after replacement and started quickly. Battery light is on and voltage gauge is low (half way between 9 and 14, assume this to be around 11 but haven’t verified with external meter). Remains so on own power after charging from running vehicle via jumper cables to ensure fully charged. Guage reads higher with jumper cables attached but not quite 14.

Insulated boot on the ground cable appeared to be potentially interfering with cable making direct contact with battery terminal (vs just the bolt). Boot was partially removed prior to reinstallation to ensure proper contact.

I looked for TSBs and searched the forum. Found that parasitic drains can be problematic with this vehicle and the visor light sometimes sticks on but believe these to be unrelated.

The battery light was on and the voltage guage low for several miles the other day (started fine) then it jumped up to 14 and seemed fine until the incident above. My best guess is the alternator but I wanted to check in here before spending the money.

Any feedback is much appreciated.

Thanks for reading

2

Surely sounds like an alternator to me but you don’t have to guess. Many auto parts stores will test them for free. If you have a multimeter/voltmeter you can do a quick check easily. With the engine running measure voltage directly at the alternator. If that looks good, now measure at the battery. If that looks bad then you have a cable problem.

At the alternator & battery both you should see something from 13-15V. If you measure while putting on a load (e.g. headlights, blower motor) it should stay above 13.

If you see anything less at the alternator then you need to replace it.

3

Found the dvm - 11.8 at batt and alt with engine running and lights on (12.2 off). Replaced alternator and now fine as expected (~14V). Appreciate the feedback - doesn’t make it any cheaper but helps with the “what if it’s not” factor.

Thanks again