87 300sdl --No Crank, No Glowplug lites= Battery reads 14.2 V
 

Hi guys--

Looking for places to start troubleshooting

Drove fine 5 days ago
Now weak -- w key in GP warm position
Weak buzzer sound/weak Battery lite/ NO GP Lite at all// NO CRANK at all
When I turn on headbeams--weak lites

Checked Battery (which is 1 years old) and with Car NOT running--
14.2 V-- Which seems like the volts that should be showing with car Running
NOT with car OFF

Any ideas on what to do next? BTW-- Alternator was replaced about 10 months ago.

Thanks!

What voltmeter you are using? Was it calibrated? Try measuring a fully charged ( old or new ) battery and compare.

I would suggest you replacing the battery and try again. 14.2V doesn't make sense with car not running. It should be around 12.5V.

If your battery is showing 14.2v with the car off then something is wrong. The alternator may make that when running, the battery shouldn’t be showing that with the car off.

You need to get your measurements working right and then go from there.

I was remembering a fully charged auto battery to read 12.8 volts. google informs me that 12.6 is the correct number. You shouldn't see a voltage higher than that if the battery is not on a charger or the car running. Most of the autoparts chains will check a battery for free. That would be my next step.

The full voltage is dependent upon chemistry and temperature. AGM also rests at a slightly different voltage too.

Regardless, you’re looking for between 12.55 and 12.75V typically. They also hold a surface charge that’s marginally higher, which will bleed down naturally over time, since lead acid batteries self discharge.