I have a 2000 Blazer 4WD, 167K miles. The other day the battery light on the dashboard came on while it was warming up but everything else was OK. I drove it up the street and the light turned off. The battery measured 12+Volts, after starting, the battery and alternator measured OK (I can't remember the voltage numbers but it was telling me the alternator was OK). The next day the battery light came on again and this time the gas gauge needle stayed at zero.The voltmeter was at about 11V. After driving it a couple blocks the battery light turned off and the gas needle jumped up. Today when the battery light comes on the gas gauge needle stays at zero, the RPM needle is at zero, all gauges go to zero. When the battery light turns off all the gauges operate OK. The last incident the battery light turned on, all gauges were at zero, and the radio was cutting out. Voltmeter at 9V. So it seems it's getting worse. Right now the short story is: when the battery light turns on all gauges go to zero, radio cuts out, headlights are weak. When the battery light turns off everything is normal.
Can it be a bad ground? How do I find it? The wind chill has been -40 so I need a quick fix.
Thank you

 

Where are you measuring the voltage when the battery light comes on (where are you putting each meter probe)?

George

 

Measured with a MM on the battery posts

 

Given that your measuring the voltage at the battery posts there are only two things that can cause a battery to spontaneously go from 12 volts to 9 volts - a failing battery probably with a shorting cell or a massive short drawing hundreds of amps. I would have the battery load tested and if you have a clamp meter with dc amps, check the current draw on one of the battery cables near the battery during an event.

A fully charged battery is 12.6v, what are you measuring?


George