You can see in my sig that my Ex is an '03 w/ a 7.3L. In the last couple of months I have been having a problem with her.

Someone goes to start her and there is not enough power. The batteries are dead.

We get out the cables, connect her to a power source, let the source build up some power, and she starts up. Then she runs well for days. Starts regularly. Like nothing ever was wrong. Then, suddenly, low battery power, not enough to start her.

...Power source, let it charge the batteries some, turn the key, starts right up. Runs great for days. Suddenly.... It's like the movie "Groundhog Day".

Since the batteries are only 3 years old I am thinking they are okay. They work day after day. The alternator must be working, Right? She runs well once started. The alternator charges the batteries so she works well for days.

The alternator is only two years old.

I'm stumped.

Ideas? Thoughts? Comments?

 

Sorry, no guessing allowed!

Grab a multi-meter and check the voltage output of the alternator with the engine running.

With the engine off, disconnect one battery and check the voltage output of both batteries.

Check the grounding cable to make sure there's a good ground/contact where it attaches to the body.

Stewart

 

One battery may be bad. Have both batteries and alternator checked just as Stewart suggests. Also, when you take your positive battery cables off of the batteries. Bend them. If you hear a loud 'cracking' or 'fracturing', then you need to replace the positive battery cables. The corrosion is up under the wire coating. That was all that was wrong mine a few years ago.

 

Mine did the EXACT same thing last year. The alternator was not putting out enough voltage at idle...I measured it at 10.5 volts. This created a slow draining effect on the batteries. Replaced the alternator (takes 10 minutes), and no problems since.

 

Thanks folks. I will check into the alternator, batteries, and cables. This what I was thinking. I had simply talked myself out of it since the alternator and batteries are relatively new.