Have a 5 yr old battery that was working fine until yesterday. After 3 hrs going 65mph, I noticed the gauge dropping to about 10 V. I turned all acessories off and it rebounded to 14V. But putting a load on it ( passing cars about 70-75mph), she would again drop to 10V. After staying at 60mph, she would go back to 14V. When I got home, turned car off and restarted her, she groaned alittle but started up. This morning I started her and it started right up. I was going to check all connections. Alternator is 5 years old as is the battery. Any tips? I think battery is starting to fail. Any agree? Thanks for all feedback.

 

5 years? No matter what else, replace the battery. Also, have the alternator tested after you get the new battery in.

 

I guess I'm use to the old days where a battery would last longer. Different times; more electric junk on today's cars. testing alternator- any web sites on quick checks I can do at home before I pull it out and bench test it? Thank you.

 

AutoZone or Advance Auto will test the alternator on the vehicle for free.

 

These newer batterys are junk they use cheap dividers in them that can fail abbruptly. My last battery was fine one morning, then like half power the next with a buldge in the side.

 

What you are looking at on the dash is NOT battery. It is charging system ie; alternator output. If you have low readings it generally indicates charging problems.

 

5 years is starting to push it for most modern batteries. Though it does depend a lot on what kind of battery it is and where you live.

Living in WI with sub zero temps in the winter and (usually) boiling temps in the summer, a standard off the shelf battery generally lasts me 3 years in my trucks. It can also depend on the vehicle that it's in.
My 92 olds usually gets 5-6 years, but that thing takes so little to turn it over that I'm literally able to jump it with a half dead lawnmower battery.

However, with voltages jumping around in the way you described the voltage regulator inside the alternator is suspect and probably killing your old battery. You can take it in to autoclone and have it tested in the truck if you like.

Thankfully popping out an alternator in most of these trucks is a piece of cake. Just remember to make them test a new one first before you bring it home. I've seen way to many brand new alternators brought home and installed only for them to not work. That can be a real head scratcher the first time it happens to you.

 

In upstate NY I generally figure on no more than 5 years for a battery. Take a good look at your belt. Sounds like a glazed belt.

 

Well, new battery, same problem. I 'm going to pull the alt out and bring it in for testing....I have a feeling I will be replacing it. I will have them check the new one before buying. Duralast? with lifetime warranty; the autozone has. Thanks for all the great advice!