Need help!

Replaced my battery in July after it just completely died for no apparent reason one day. It was 10 years old, so didn't think anything of it. A little over a week ago, I noticed the voltage guage had gone from about 12.5-13 down to 12, and the battery and brake indicator lights on the dash were illuminated. Over the next couple of days, the voltage decreased more and I was told the alternator was bad.

I had the alternator replaced yesterday and had the battery charged. Again, dash lights for battery and brake are still on, and the voltage is hovering around 12. If I'm in gear and at a good speed, it will increase to almost 12.5, but drops back to 12 if idling. I took the truck up to get everything tested, and was told the alternator is not putting out enough voltage and should be replaced. However, they also said something about a voltage meter (?) being bad.

I know very little about cars and need direction. Does this truly sound like another bad alternator, or could it be something else?

Thanks!

 

Measure the voltage on the battery terminals. It should read 13.5-15 volts with the truck running.