Electrical Mystery Tour

Jun 21, 1997

RAY: There I was in my office reading through the technical service bulletins, having nothing better to do.

TOM: Since there were no customers. And in case someone came in you might know the answer.

RAY: Exactly. And I was reminded of a Puzzler of a car we had many years ago. I don't remember exactly the car, but I think...

TOM: Was it during my tenure as Chief Mechanic?

RAY: Yes it was during your tenure as uh...never mind.

TOM: Floor sweeper and Chief Mechanic.

RAY: We had a customer that came in with a Dodge Van and the problem was that the battery was going dead. And he had had of course a new battery put in because when he first noticed the battery was dead, someone said, "Hey, you need a new battery". So there he bought a new battery and plunked it in. And a few weeks later the battery was dead again. He went out to start his car in the morning, turned the key, and click click click. Nothing would happen.

TOM: Not even RRRRR? Staight to the clicks.

RAY: Right to the clicks. So he took it to his neighborhood mechanic. The neighborhood mechanic said, "You need a new alternator."

TOM: No, no, if he had gone to a new guy, he would have said you need a new battery. He probably went to the same guy who knew he couldn't get him for another battery so he said, "Ah -- alternator. "

RAY: So he puts in a new alternator and everything is alright for a few weeks, then lo and behold, the same thing happens.

TOM: Ooh. Did he go right to the clicks again?

RAY: Right to the clicks or the clacks this time. I don't remember. So, a new battery. New alternator. Goes back and has another alternator put in, another battery. All of this on warranty of course. And every time they're putting in best quality parts, everything works. Put in a new voltage regulator, make sure the belt is tensioned correctly. There are no drains on the system. You might think - - Ah ha! When he's sitting there, the dome light is on, or the glove compartment light is on overnight and it drains the thing out.

TOM: Did this car have an 8-track player?

RAY: No it did not have an 8-track player. So there he is with this problem here, this electric system all of whose parts are perfectly OK. And we will stipulate that they're all OK.

TOM: All of the components.

RAY: All of the components in the charging system are fine. All of the wiring is fine. The battery is fine. There are no drains on the system. Yet, every two weeks or three weeks, the battery goes dead. If it's jumped it starts, it runs if you charge up the battery fully. Even without doing any other repairs to it, it may run again for another two or three weeks until finally one morning it's dead.

TOM: Kaput. Click, click, click.

RAY: The question is -- what's going on here?

TOM: Well we know what's going on. He's spending lots of money. Beyond that -- what's going on technically?


RAY: Well, the truth is there was probably nothing wrong with the original battery. What was wrong was the alternator was in fact faulty. The first alternator. The mechanic who replaced the alternator put in the right alternator, but it had the wrong size pulley.

TOM: Ha. Ha. Ha.

RAY: Ha. Ha. Ha. The pulley was too large in diameter and wasn't turning fast enough.

TOM: Yes. Big pulleys turn slowly and little pulleys turn fastly.

RAY: And you say well, what difference could that possibly make? Well, the difference it could make...

TOM: Right hand rule! It makes all the difference in the world. Everyone knows that the amount of electricity that you make, thanks to Michael Faraday, is a function of how fast the moving conductor is moving.

RAY: Right. It becomes especially important if you're driving around all the time in stop-and-go traffic.

TOM: And was this the case? That's the piece of information you left out?

RAY: Well, yeah. I had to leave it out otherwise it would have been too easy.

TOM: The truth is if you were driving 60 miles per hour this would not have happened.

RAY: Right. It would have been certainly adequate. To make it even worse, it was stop-and-go driving in the winter time when you have the headlights on, the heater on, the heated seats, the rear-window defogger...

TOM: The graphic equalizer.

RAY: The graphic equalizer.

TOM: The 8-Track tape player.

RAY: The Cuisinart.

TOM: Electric Shaver. The Juice Man.

RAY: Juice Tiger.

TOM: Do you have an adaptor for the Juice Tiger? And an iron. I always try to get my clothes done when I'm driving.

RAY: Yes, I can see that.

Get the Car Talk Newsletter