MINNEAPOLIS (WCCO) — It is the mantra of the professional mechanic. You do diagnostic testing of a vehicle to determine what needs to be fixed, rather than just replacing the parts that are “probably” causing the trouble.

After 40 years of working on cars (as a hobby), the “test, don’t guess” lesson is one I am still learning.

Case in point: my wife’s 2005 Ford Focus recently told her it had a “low battery”… at least that’s what the CD player said after it quit playing. She also noticed dim headlights, and wisely came home immediately.

I knew the battery in the car — at 53,000 miles — was probably the original battery, so I got a new one on the way home from work that evening, and installed it right away.

The next day, after several short trips, her same battery-trouble symptoms returned. I now knew the problem was almost certainly the alternator, so I put the battery charger on that night so the car could be driven (cars will run for some time on a good fully-charged battery) to the shop the next morning.

What I heard when I got to the Ford service department was that it is a good idea to do a load test on a vehicle’s battery at least once a year… more often if you know the battery is more than a couple of years old. I was told the alternator of the Focus burned itself out by working too hard to charge the failing battery.

Cost of a new battery: Less than $100. Cost of new alternator, installed at dealership: $860.

Should I contact a regional customer service person from Ford & tell them I am disappointed that a five-year-old car had to have the alternator replaced? I think I will. I have never had a vehicle that “ate” its alternator because the battery was dying. Dead batteries happen, and the car should be able to deal with that fact.

Am I going to buy a battery load tester?

Yes I am.

The basic model costs about $80, or 10 percent of my alternator replacement. And I will test the batteries on all my vehicles (at least the ones that run) about twice a year.

  1. richard says:

    The alternator “puts out” at a costant rate and I belive the voltage regulator controls how much charge reaches the bat. The explanation sounds bogus to me. I would get a second opinion and chalange the diagnosis post haste. Sounds like BS to me.