Fire and Ice
Options, options and more options
The early days of the anti-idling movement took imagination and know-how because there were no manufactured solutions. Today the industry has moved to the other extreme with countless options and spec'ing solutions, making it easier to design the right system for your needs.

By Paul Abelson, senior technical editor

Times have certainly changed as anti-idling regs and high fuel prices have turned up the heat on trucking operations to keep costs down and cabs comfortable.

The earliest idle-reduction devices were heaters, back before the Teamsters recognized a need for air conditioners and included them in the master contract. Left off in sub-zero temperatures, engines would cold-soak overnight.

Engine coolant heaters would keep blocks warm enough to keep oil from thickening and to allow cylinders to heat so fuel could ignite. Back when there were no anti-idling regulations, it was a tough sell to get truck owners to part with $1,200 to $1,500 for an engine heater. It didn’t even keep the driver warm without running heater fans full blast, draining the batteries. Drivers could rely on an electric blanket, also running the batteries down, or spring for another $800 or more for a fuel-burning cab air heater.

It was far easier just to idle the engine. Then there would be no concerns about the engine starting in the morning.

A few enterprising owners bought Ford Pinto and Chevy Vega engines from scrap yards. They fabricated mounting frames from angle iron. The engines were throw-aways, replaceable for under $100 each. They ran on gasoline, but drivers didn’t mind having the extra tank.

The first fuel-burning bunk heater, Stewart-Warner’s Hot Box, also ran on gasoline. These “pony engines” with air conditioner compressors and alternators included with the engines were the earliest truck auxiliary power units.

Soon, pioneers like Ray Miller at Double Eagle Sleepers and Rex Green at Pony Pack (now APUs by Rex) were manufacturing APUs with diesel engines. Years later, with anti-idling regulations on the horizon, many competitors entered the market.


APU installation still involves running refrigerant hoses from the compressor to remote components – the evaporator in the cab, the condenser behind a fan and the receiver-dryer where it will fit.

Heat was provided either using electricity or by plumbing the APU’s cooling system into the main engine. The mass of the big block absorbed and dissipated the heat from the small diesel, leaving coolant warm enough to circulate through the cab’s heat exchangers. Running fans was no problem since the APUs alternator supplied enough current.

The problem with this type of system is that if there is a failure in the main engine’s cooling system, the APU’s engine goes down, too. That means there’s no backup source for heat or air conditioning. The same is true if the truck’s and APU’s air conditioning systems are tied together and there is a hose or clamp failure.


Rather than using mechanical power with the APU’s engine turning the A/C compressor, many air conditioning systems have been designed to run on electric power alone.

This offers several advantages.

Installation is simplified because all hoses and plumbing are factory installed, inside a protective housing. There is greater flexibility in locating units, since it is easier to run electric wires than to run refrigerant hoses. With pre-assembled units, installation mistakes are virtually eliminated.

These electric all-in-one units that combine heat with air conditioning do have their compromises. Placing them in the best location for A/C means they may not be well placed for heating.


Another alternative to the APU or all-in-one is the generator set. Gensets do one thing; they create electricity. The electric current can then be routed to anywhere it is needed. It can drive an air conditioner in one location and power a heater in another.

And, when it comes to keeping comfortable in the cabs, we tend to think of HVAC as being either air conditioning or heat, losing sight of the “V.” At temperatures between about 60 and 80 degrees, ventilation can save money. Various devices are available, ranging from rooftop weatherproof exhaust fans to window screens with fans mounted on the frames.

Finding the right mixture of comfort systems and supplied power can be tricky, but not impossible, with the wide array of options on the market today – and at least you’re not heading to the scrap yard looking for another Vega engine. LL