Teacher may be ahead of his time with hair dryer heater idea

Dear Car Talk:

I taught auto mechanics for over 30 years to high school students. In the 1980s, when I was explaining how the resistors in the fan blower worked, I compared it to a hair dryer.

That gave me an idea. Why not add a hair dryer type of heating element in the car’s ductwork for instant heat to the passenger compartment? It could reduce or turn off as engine heat increased until it was no longer needed.

I didn’t pursue this idea because batteries back then were overworked beyond their capacity and heating elements draw a lot of power from the battery.

Fast-forward almost 30 years to today, and you have remote starting devices that are installed for hefty prices. These wear out engines, pollute, use gasoline so reduce gas mileage and have too many parts that can fail.

Today you have heated seats, heated rearview mirrors and mega sound systems guzzling up power from our batteries, so they can’t use “the battery can’t handle it” anymore as an excuse.

I would guess that installing my system in the air duct would cost less than $20 at the factory and cost little to operate. Can it be done? – Raymond

RAY: Anything can be done, Raymond. I mean, look – they let me write a newspaper column. That doesn't mean it should be done.

A typical hair dryer uses about 1,200 watts. And realistically, you’d need at least a pair of them. So you’re talking about 200 amps at 12 volts. That’s a pretty significant load on the battery.

It wouldn’t kill the battery in 10 or 15 minutes, but if your battery were old or marginal, and it was a cold day (which it obviously would be), you could weaken it to the point that you’d have trouble starting the car. And wouldn’t that stink?

Of course, once the car is running, you could pull 200 amps from the alternator and the battery combined, and that wouldn’t be a problem. So it could be a way to get some heat right away, once you start the car, but before the engine is producing usable heat.

The larger issue is that heating the air is the least efficient way to keep the driver warm.

Take a typical sedan. Say it has about 20 cubic feet of interior volume. You’re taking up about 4 of those cubic feet, and yet you’re wasting a ton of energy heating up the other 16 cubic feet to 70 degrees.

In contrast, radiant heating (seat heaters, steering wheel heaters, rear window defroster) use far less power, and deliver the heat precisely where it’s needed: to your tuchus and key surrounding areas.

But here’s the good news, Raymond: Your idea actually makes more sense for electric cars, which are getting more popular every day. Here’s why. Electric cars don’t have internal combustion engines, which give off heat. So they already use electric heating elements to heat up the cabin.

And on a cold day, with a simple remote control, you could run the heating element while the car is still plugged into its charger. That would preheat the cabin without eating into the car’s battery reserve and driving range.

So it’s a great idea, Raymond. You were just 35 years ahead of your time and working on the wrong propulsion technology.

Tacoma truck’s problem is more than ‘idle’

Dear Car Talk:

My wife drives our 2002 Toyota Tacoma. It’s a V6 with 180,000 miles.

She reports that the engine will sometime die when she shifts from park to reverse. It doesn’t happen every time, so it’s hard to pin down. It seems like it’s worse in hot weather, and usually happens when the AC is on. A quick bump to neutral and the truck starts back up fine.

I bought the truck new, and it's in excellent shape otherwise, but now I'm worried about future transmission problems. Suggestions? I always enjoy your column! – Ronny

RAY: I doubt it's your transmission, Ronny. Which disappoints me because I have a boat payment due at the end of the month.

More likely, something is causing your idle speed to drop. And when you put the truck in gear, which puts an additional load or “demand” on the engine, the idle speed drops a little bit more and the truck stalls.

I’d check the operation of your idle air control. When you use a major accessory like the AC – one that also places a big demand on the engine – the computer is supposed to tell the idle air control to boost up the idle speed to prevent it from dropping too low and stalling. It’s like stepping on the gas pedal a little bit.

Your idle air control may not be working the way it’s supposed to when the AC is on. It could just be dirty.

Even more likely, though, is that you have a vacuum leak. Vacuum leaks are very common on older cars and would also cause the idle speed to drop. Since it seems to happen only when you shift into reverse, it could be related to how the engine twists when you put the truck in reverse.

If you open the hood and watch while someone shifts the truck from park to reverse, you’ll see that the engine actually moves a little bit in one direction. When the truck is shifted from reverse to drive, the engine will move in the opposite direction. While it only moves an inch or two, it can be enough to make a crack in a hose open up more or close down more. That’s what I’d look for.

How do you do that? We’ll have one guy plant his foot on the brakes and put the truck in reverse. And when the engine begins to stumble, we have another guy go around with a wand that’s attached to a cylinder of propane. And that second guy will shoot a very small stream of propane gas around the areas where we suspect a vacuum leak.

When the propane encounters a vacuum leak, it gets sucked into the engine through the leak, and raises the idle speed. So when we hear the engine go faster, bingo, we’ve found the leak.

A vacuum leak could be anywhere, but I’d definitely check the fat, snorkel-like hose that connects the air flow sensor to the throttle body. We’ve seen that hose leak before.

And if that doesn’t work, build your wife a circular driveway, Ronny. Good luck.

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