auto maintenance February 02, 2018

Heat of the moment

As you sit shivering, waiting for your car to convert some gasoline and noise into heat, and cursing under your breath for not getting the remote start option, think of my mother, whose father went without heaters in his cars. This was in Michigan, and since the lack of a heater meant the windshield was usually frosted or iced up, he drove with the driver-side window cranked down and his head craned out to see where he was going, the icy blast chilling my mother and her brother in the back seat.

Yes, dear readers – in the forties, fifties, and even right up into the mid-sixties, the heater was an extra cost option, and though grandpa was a man of considerable means and stature, he was a puritan descendant who needed no 20th century luxuries. For decades after his death we relived the scene in the Ford showroom when Grandpa discovered that his new 1971 Ford Maverick (3 on the tree, no power steering) came with a heater and he had no choice in the matter.

“But Mr. Howes, you’re not being charged for it!” pleaded the young heavily-outmatched salesman holding the invoice. “Young man,” Grandpa replied, “I‘ve been around a while, and I know damn well I’m paying for that heater whether it’s on the invoice or not!” I don’t know whether Grandpa ever turned that heater on, but I’m sure my cousin who inherited it and drove it the next 10 years did.

Getting heat in a car should be fairly easy since a gasoline engine is only about 35% efficient in energy conversion, the other 65% percent exiting as wasted heat. A large part of that wasted energy is the cooling system of a car. The intense heat in the engine’s combustion chamber would quickly destroy the engine if not controlled. So the engine is honeycombed with passages through which liquid coolant is pumped by a water pump. The coolant takes the heat away from the engine and dissipates it into the air through the radiator. The coolant then continues its endless circle back through the engine.

So it didn’t take long for car designers to place a second small radiator in the passenger compartment, encase it in a box with a fan blowing through it, and voilà, the modern automotive heater was born. And again it didn’t take long for the engineers to duct some of that hot air onto the inside of the windshield, and the windshield defroster was born.

The systems were simple, well-built, and thus extremely reliable. The heater core itself was copper (as was the radiator). Now those components are plastic and aluminum. The ducting (floor heat or windshield defrost) was controlled by a metal door moved by a cable like the ones on your bicycle. A heater control valve regulated coolant flow through the heater core. This was simply a variant of the faucet in your sink, increasing or decreasing coolant flow by means of a cable. The blower had two or three speed choices and was as loud as one of the bonnet hair dryers in a fifties women’ hair salon.

Ah, but with affluence, people want a little more.

Now when you turn on your heater, assuming the engine has gotten warm enough to produce heat, you are making a request to a computer module. That module then sends commands to electric motors that move doors inside a complex manifold to give you the precise temperature you want out of the vent or combination of vents you indicate.

The blend air door mixes air that has passed through the heater core with air that has passed through the air conditioning evaporator to control temperature. Mode doors direct air to the desired vents, and in systems with separate driver/passenger controls, many of these functions are duplicated. Often the blower will come on in a gentle ramp-up so your senses will not be shocked by the sudden noise and airflow.

All this adds expense and complexity to the systems and makes them less reliable, much the way a Sears Kenmore clothes washer or drier from the sixties was often found in service 20 years later, but modern appliances rarely last a decade.
Unfortunately most of the components are installed when the car is little more than a steel frame on the assembly line. To service them once they are in the car often requires hours of disassembly and re-assembly, often with the technician having to lie in extremely contorted positions.

I suspect that in the next couple of years, a major effort will be made to find a way to provide some level of heat within a minute of starting. Probably electric, but who knows. Back in the fifties when heat was optional, one available option on certain cars was a “gasoline heater.” This took gasoline from the fuel system and ignited it in a combustion chamber connected to a heat exchange. This all took place inside the passenger compartment. A little dangerous for my tastes, but talk about instant blow torch! No waiting for heat with that.

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