5 car heaters in the test

Beate Jeske
5 car heaters tested
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E s snowed last night. It was freezing cold too, around −15 ° C. At 9 o'clock in the morning it is still −11 ° C. Our five test cars are covered in sugar and have cooled down, but there is no pardon: they still have to work. All at once and all according to the same rules.

Loud defroster

This applies to the Audi A6 Avant 3.0 TDI, BMW 520d, Mercedes A 200 CDI, Toyota Prius and VW Golf 1.4 TSI Identical procedure: scrape off the windshield, activate the temperature sensors on the inside mirror (head space) and in the passenger footwell. The respective automatic air conditioning is set to 22 degrees Celsius, and then it goes like a string of pearls across the wonderful wintery Swabian Alb with the question: In which interior does it warm to comfortably within 20 minutes?

But defrosting the windshield was not primarily the issue, but rather the medically proven comfortable temperature of 22 ° C . And that with the main focus on the headspace, because nobody likes to sit behind the wheel like Rudolph the red-nosed reindeer.

Five minutes have already passed - in the Audi, BMW and Mercedes, at least the temperatures are already positive. In the Prius there is a kind of additional 'instantaneous water heater' in the exhaust system, in the Golf with its comparatively small petrol engine there is also an auxiliary heater for warmth.

Footwell stays cold

In the depths of the footwells remains It's still frosty - from −9.1 ° C (Gulf) to −5.8 ° C (A-Class). But we hold on, subjectively warm air comes out of the vents. The water in the cooling circuits of the engines absorbs the waste heat from the units. However, as the efficiency of the engines increases, this becomes more and more difficult.

Nevertheless, the heating output of the BMW 520d, for example, after ten minutes of driving is 5,200 watts, which is now fed into the ventilation system via the heat exchanger integrated in the air conditioningcan be dispensed over two cubi-meter interior. A further 1,000 watts is provided by an electrical 12-volt auxiliary heater.

After ten minutes, it gets more comfortable, even if the possible 5,200 watts of heating power of the Toyota is only reflected in 0.2 ° C. The Golf struggles to a meager 2.5, the A-Class to 3.3 ° C. The bulky winter jacket is better left on.

Meanwhile, the crews in the A6 and 5 are already thinking about a stopover to undress. 7.5 ° C slowly but surely make you forget the frustration with Father Frost. Except for the cold feet in all cases, because the footwells are pretty quiet.

But then the Prius gets going. Within five minutes he pushes over 8 ° C on tiptoe. However, he neglects the headspace. Even the Golf is still weak after two thirds of the driving time, while the BMW accelerates.

BMW and Audi with the most powerful heaters

Not that the 520d storms away from the quintet. We drive gently in formation at a maximum of 80 km /h overland. But after 15 minutes the temperature sensor attests the BMW 13.4 ° C. Only the Audi is also in the double-digit range (11.1 ° C).

On to the final spurt, a head-to-head race like the one in the DTM seems to be looming. The goal is reached immediately, then we'll see who fires the fastest at the specified 22 ° C within 20 minutes and around 15 kilometers.

None. With 17 ° C in the head and 13 degrees in the footwell, the 520d has already heated up its driver properly, the A6 3.0 TDI Avant is just behind. And the comparatively smaller and much cheaper A-Class pulls itself out of the cold affair very well.

In contrast, the Prius driver has warm feet, but keeps the coolest head at the end of the journey. At just over 10 ° C, the Toyota is almost as far away from the targeted temperature target as the Golf. Both heaters get up to speed slowly at first, work hard for a short time, then flatten again.

It's still −5 ° C outside. But no matter now, we're finally sitting inside in the warm - with a hot cup of tea to finish off.

How we tested

For once, the winter weather played into our cards for this test. The five test cars spent a night outside at −15 ° C. The next morning the temperature sensors mounted on the interior mirrors and in the passenger footwell were started. With the five climate control units preset to 22 ° C, we set off on a restrained journey together. A good 20 minutes later the accounts were settled and the data stored in the measuring systems were evaluated on the computer. And since the acoustics also count for well-being in the interior, the noise level was also measured in every vehicle during defrost, i.e. with maximum ventilation of the windscreen.

This is how the standard heating system

works wellOne third of the efficiency of an internal combustion engine is actually used for locomotion, the rest is dissipated as waste heat or exhaust gas, which for the most part also means heat. This released energy is converted into warm air for the interior by the heated cooling water by means of a heat exchanger. The constant efforts to increase the efficiency of the internal combustion engine in order to save fuel have an inverse effect on a lower heating output. This means that modern downsizing or more efficient diesel engines often require an additional electric heater.

The efficiency of diesel engines has been optimized to such an extent that they hardly produce enough heat for heating. This also applies to electric and hybrid cars. They need additional heaters to compensate for this deficit. There are two types: The fuel auxiliary heater works like an auxiliary heater - but only when the engine is running. Some of these devices can even be converted into a fully-fledged parking heater. The electric auxiliary heater works either as a water heater (similar to an immersion heater) or as an air heater, which is built into the ventilation system and heats the air flowing past for the interior.


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