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Voltmeter reading

Have a 2007 Chevrolet Suburban. The voltmeter reading varies from 13 to 16 volts, no obvious reasons for changes in the reading. Chevy says there are a number of different inputs that determine what the reading should be, such as battery temp, etc. On older cars you could use the voltage to determine when something was going wrong with the electrical system. Other that a complete loss of alternator output, can you use the reading to diagnose electrical problems, such as a bad or dying battery?

Vehicle gauges are not very accurate. I would use a digital voltmeter to check your battery voltage while the engine is running. A reading of about 14 VDC while the engine is idling is about average.

+1 for MM

+2 for MM.
I should add that many parts stores will test your battery and your charging system for free. Call around.

Our two late model GM cars, one with a voltmeter, also show wide variations in voltage. The car voltmeter is quite accurate; is within about 0.1 volt of my ICOM DMM and also a cigar lighter plug-in digital voltmeter from WM. I can’t explain the 16 volts but I have seen 15+ volts at times.

Possibly your Suburban works like our cars. After several miles while riding on the freeway, the voltage settles down to around 13.6 volts. GM does this to reduce the mechanical load on the alternator to save a little fuel. It is also less stressful for the battery to be kept at a “float” charge voltage level. You could call this Computer Controlled Smart Voltage Regulation.

Regarding analysis, my intention is to learn the anticipated voltages of the new setup and then watch for a voltage that is not expected. Other than that, you can buy an inexpensive battery tester from Harbor Freight. It has a loading resistor and also measures voltage during the test. You could test a new battery, record the reading and then watch for changes when there is doubt of your battery’s lifespan.