It’s safe to use seat heaters if stranded in snow

Dear Car Talk:

I know it's hot out, but I have a winter question. All my life I've heard that if you get stuck in the snow and don't know when you'll be rescued, in order to keep from freezing to death you should run your engine for 15 minutes per hour and make sure the tailpipe is cleared of snow. What about cars equipped with seat warmers? Can I run them all the time without running down the battery, or only while the engine is running? What about if I have a passenger or just want to keep my pumpkin spice latte and cranberry scone warm for later? Can I run both of them? Thanks. – Ralph

RAY: Your seat warmers are powered by electricity, Ralph. If the engine is running, the alternator is producing so much extra electricity that the seat heaters can run indefinitely. But if the engine is not running, the seat heaters will run off the battery. And eventually, that would drain the battery.

How long will that take? Well, I’d take an educated guess that the average seat heater draws about 4 amps. That’s about as much as your car radio uses. And seat heaters don’t draw 4 amps continuously; they cycle on and off at a frequency that depends upon whether you set them on low, medium or high.

But let’s take the worst-case scenario and assume that your seat heater runs continuously for an hour. That would use about 4 amp hours. Your battery probably is rated at 600 amp hours or more when fully charged. So there’s almost no way it’s going drain the battery to the point that you can’t restart the car in 45 minutes.

And if you run the engine for 15 minutes every hour, the alternator – which makes 80 or 100 amps – is going to recharge the battery and more than make up for the power that the heated seat uses. In fact, if you cycle the engine as you describe – 15 minutes on, 45 minutes off – you probably could safely use both seat heaters indefinitely. Or until you run out of gas.

Now, I can’t guarantee this. Lower temperatures reduce battery life. An old battery or a faulty charging system could alter the equation. And it’s always wise to exercise caution in a situation that could result in your passing through the digestive system of a grizzly bear. But my guess is you’d probably be fine using both seat heaters until the mounted police arrived with their St. Bernards and flasks of Bartles and Jaymes.

If you make it through this imagined Armageddon, write to me and let me know I was right, Ralph.

Plugged-up catalytic converter unlikely to cause permanent damage

Dear Car Talk:

I have a 2012 Ford Fiesta five-speed. The check engine light is on, and the computers at AutoZone and Big O say it's the catalytic converter and oxygen sensors. This will cost me about $850 to fix. I'm pretty middle class. Since I'd rather buy lottery tickets with my money, can I just have a guy take out the catalytic converter and put in a straight pipe? We don't have emissions testing where I live, in Indiana. Please tell me how dangerous it is to drive with a "bad" catalytic converter. Will it destroy my engine? Will fumes back up into my front seat and make me drive into opposing traffic? Thanks. – Marlyce

RAY: A 2012 Ford Fiesta … you lucky devil! Here's the good news, Marlyce: Driving with a plugged-up catalytic converter shouldn't permanently harm your car.

At some point, if the converter gets completely plugged up, it’ll diminish your power. And eventually it’ll prevent the car from running at all. It’d be like having a potato in your tailpipe. Then you’ll have to remove the converter if you want the car to run again.

As long as the exhaust system is intact, without leaks, you won’t get any fumes in the passenger compartment. Of course, the same can’t be said for the poor jamokes who are driving behind you.

The bad news, Marlyce, is that it’s illegal to remove your catalytic converter. Federal law sets baseline emissions requirements for all cars in the United States, and gasoline-powered cars can’t meet those emissions requirements without catalytic converters.

States are welcome to set emissions limits that are more strict than federal law, but not less strict. So you would be a criminal, even in Indiana, Marlyce. On the plus side, stripes can be slimming!

Now, in reality, since Indiana does not require emissions testing, it’s unclear to me how you would ever get caught. But you’d still have to wrestle with something known as your conscience.

So it’s your choice. You could save $850 but increase the chances that you, your kids and your neighbors will get asthma, brain tumors and mutated DNA. Or you could spend the $850, sleep well at night, but wake up every morning and wish you had an extra $850.

Actually, you don’t say how many miles are on your Fiesta. But emissions components – including catalytic converters and oxygen sensors – are all warranted for eight years or 80,000 miles. So if you’ve got 79,999 miles on the odometer, have it flat-bedded to the dealer and get that stuff replaced for free.

If you’re out of warranty, I can’t tell you what to do, Marlyce. But if I could, I’d tell you to be a good citizen and replace the converter.