At only 27 of the 40 garages did mechanics tell Mr. Schneider that he had a disconnected battery cable, the very problem to which he had pointed them by saying his car didn’t always start. Only 11 mentioned the low coolant, a problem that can ruin a car’s engine. Ten of the garages, meanwhile, recommended costly repairs that were plainly unnecessary, like replacing the starter motor or the battery. (Tellingly, his results were in line with what the Automobile Protection Association found when it performed its experiments in Canada.)
Note that this is similar to the experiments run by 60 Minutes that exposed a similar problem at Sears Automotive.