Battery replacement is easier if left to the pros

Dear Tom and Ray:

We have a 2006 Chrysler Town and Country van. Is it OK to buy and replace the original battery ourselves? Or is this a job for the professionals? We just bought and replaced the battery in our 5-year-old John Deere lawn tractor with no problem, so I am thinking we could do this ourselves, too. My husband says no - that things have to be reset on a vehicle. Is he right? We plan to replace the battery before winter either way; it was sluggish on cold days last winter. We both read and learn from your column. Thank you. - Jan

RAY: Well, it's something you CAN do yourself, Jan, but I'm not sure it's worth it for the small amount of money you'd save.

TOM: The downside of replacing the battery yourself is that you lose all of your stored settings. That means all of your radio-station presets will play 87.9, your power seat settings will be all the way back in the tooth-drilling position, and if you have a navigation system and you hit the "take me home" button, you'll end up at the Chrysler plant in Windsor, Ontario.

RAY: Obviously, all of those settings can be re-entered. But you'll also lose the memory in your engine monitors. That's what your husband probably is referring to.

TOM: Your engine's computer keeps a record of things like engine misfires and oxygen-sensor performance, and confirms that, over time, your emission- control system is doing its job. And if you remove the battery, those settings disappear.

RAY: The computer will start recording them all over again as soon as the new battery is installed. But if you happen to need a state emissions inspection soon after changing the battery, you may be turned away. The computer requires a certain number of engine on-and-off cycles to confirm that your emission controls are working. And if you haven't driven enough cycles, you may have to go away and keep driving for a while before you can get a sticker.

TOM: To avoid this, you can go to an auto-parts store and buy, for $15 or $20, a little device that takes a 9-volt battery, plugs into your cigarette lighter and provides enough power to maintain your battery settings while you swap the batteries. We've got a professional version of that at the garage, which plugs into computer's data port.

RAY: But for a little more than that, you can have a local garage or Sears do the whole job for you, including saving your settings, disposing of the old battery and taking responsibility if they hook it up backward and set your car on fire. And you get to drink their putrid coffee in the waiting room to boot.

TOM: So it's up to you, Jan. But do the math first. Get a price from your local shop and see how much it'd charge you for the whole job. Then get a price on the battery, the settings saver and a bottle of Gojo to wash the grease off your hands when you're done, and see what the real savings is before you decide. Got a question about cars? Write to Click and Clack in care of this newspaper, or e-mail them by visiting the Car Talk Web site at www.cartalk.com.

© 2010 by Tom and Ray Magliozzi and Doug Berman. Distributed by King Features Syndicate, Inc.