Mistaken diagnosis comes with a bill

Dear Car Talk: I have a 2005 Mercury Sable with 37,000 miles and a brand-new battery. I recently took it to a local ASEcertified auto repair shop for starting problems.

After having the car all day, the service manager gave me a written diagnosis, in which his mechanic claimed there was a slow current draw within the wiring inside the instrument panel. I was told that it would take two weeks for the panel to be sent away to have the wiring refurbished, at a cost of about $800.

I paid for the diagnostic time, which was $120, and took the weekend to think about the larger repair. I decided to get a second opinion, so I took it to a Ford dealership, and quickly got a diagnosis as merely a faulty starter. They replaced my starter, and now the car starts great.

I called the owner of the ASE shop to tell him that his mechanic had grossly misdiagnosed my car. I asked for half of the diagnostic fee back. This request was rejected because he said the mechanic worked all day tracking down this wiring panel problem. What do you think?

The first mechanic went down what is called a rabbit hole, Danny. I’m sure his intentions were to solve your problem and make you happy. But he ended up wasting a day and $120 of your money.

My guess is he suspected the starter, but when he tested it, it worked fine. I’m guessing that your “starting problem” was intermittent, right? Your car would start sometimes, and not others. That’s why you brought it in. That’s very common.

So when the battery and starter tested fine for him, he checked for a current drain and found that something was drawing power from the battery when the car was turned off. He assumed that was the cause of your starting problem, that something was draining your battery to the point where it did not have enough power to start the engine. So he traced it as far as the instrument panel, and then ran out of daylight.

What he might not have known, but probably should have, is that just about all cars these days have things that draw current when the car is off and the key is in your pocket. Things like the alarm system, the main computer, the bodycontrol module, the radio presets and the fuel-vapor recovery system all can require some sustaining power, depending on the car. If you leave any modern car for two to three weeks nowadays, it won’t start, for exactly that reason.

So he accurately diagnosed a current drain, Danny, which is good. But what he diagnosed was a normal condition that has nothing to do with your starting problem, which is bad.

So you took it to the dealer, and the dealer knew, from experience, that the starters in these cars (like many starters) often fail intermittently. And the dealer made an educated guess that the starter was failing, and he replaced it (or maybe he just got lucky and saw it misbehave while he was testing it).

In any case, your car has been starting reliably ever since. I hope, since you wrote to me, it’s still starting reliably — in which case the dealer guessed correctly. If your car fails to start again, then perhaps the first guy was actually on to something. And maybe the current drain was not “normal” but was caused by a wiring problem.

But my guess is that the first guy did his best but, unfortunately, didn’t have the knowledge or experience to know what a normal current drain should be.

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