Battery keeps dying even though it checks out fine


#1

Also the alternator is pushing 14.2 volts and using an amp test between the negative terminal and the post there appears to be no current drain beyond normal. I think the shop guys told me it was .01

One of the two guys then suggested that the altenator was the problem, that even though it appears to be working it actually drains the battery. The battery charges when I run the car and restarts but leave it for a little while and I need a jump again.


#2

How old is the battery and did the mechanic perform a “load test” on the battery?
Was the alternator tested to verify it’s capable of producing its rated amperage output?

Also, please provide information about the car (year, model, miles, and any significant related repair milestones).


#3

The car is a 99 Mercury Mystique with 110k miles. No Major repairs ever until maybe now.
Yes, the battery was tested via Sears and I was told it passed the load test with flying colors. It is about 3 years or possibly 4 years old.
They tested to see how many volts it was producing showing about 14.2
Thank you for asking.


#4

Saying the alternator produces 14.2 volts means nothing. Did they do a load test on the alternator to prove it’s capable of delivering its rated current output when under a load?

As for the battery load test, I’m not familiar with how Sears tells its techs to test batteries. Does anyone know if they have the equipment and if they take the time to properly load test batteries?


#5

no I don’t believe so. Aside from the voltage test they assumed it was charging the battery while the motor was running because the battery always seemed to build up enough power after the car was running to enable it to restart. But then after about an hour it won’t start.


#6

These problems are not difficult when you have a correctly trained mechanic with the right equipment and a customer willing to pay a reasonable fee. Everything is spelled out in the basic automotive textbooks,it is not black magic. If automotive electrical is not your strong area I am sure there is something you excel in, then you can use that money to pay a expert,or buy the book.


#7

“Also the alternator is pushing 14.2 volts and using an amp test between the negative terminal and the post there appears to be no current drain beyond normal. I think the shop guys told me it was .01”

You’ve already answered your own question. If the battery will start the car, then not start it a little while later with no drain as you say above, the battery is bad. It won’t hold a charge.


#8

Thanks Jay. I just went over to Pepboys (Sunday doensn’t leave many options) and their diagnosics showed the battery to be bad. So much for Sears. So I bought a new battery and hopefully thats the end of this thread :slight_smile:
As for the previous comment, Old school should try reading what I said before commenting. If he had a comment to make about how easy it was not black magic and all that stuff, it would have been better directed to the Sears guys which I was more than willing to pay to solve my problem.


#9

I did read what you posted and thats why I suggested you pay someone to do this work or buy the book.


#10

I have to side with Oldschool on this one. The business model I remember at Sears doesn’t support fully trained techs using the right equipment. PepBoys is more in the Sears category than the kind of place Oldschool was referring to.

You started this thread with questions and several unknowns. We were only trying to steer you in a direction that you could more reliably understand what the issues were.