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New Day, New Way
Can’t you build your own?
Test drive of the Cascadia reveals a fleet truck with new-found comfort

By Paul Abelson
senior technical editor


Q: All these states are making new laws making us have APUs. I bet big business is lobbying the states so they can sell more. I can’t afford one. Can I build my own?


A: The earliest truck-mounted APUs were almost all home-built. Owner-operators welded channel iron into frames and mounted them behind the cabs. They used small car 4-cylinder engines from wrecking yards.

Chevy Vega aluminum engines were popular because they were light, cheap and available. At around $80 each, they became throwaways, to be replaced, not repaired if they broke. Heavy-duty alternators and air conditioner compressors were moved from engine to engine. The cooling systems were plumbed into the engine’s cooling system, so no fan or radiator was needed.

Today, that can still work. Instead of gasoline engines, older Volkswagen diesels are showing up in wrecking yards. The car diesels are heavy, though. Lightweight diesel generators are available in catalogs and industrial supply houses.

But, and this but is an important one, starting in 2008, California will issue citations if APUs and generators do not meet the strict emissions standards for the 2007 diesel engines. That means they must have diesel particulate filters. And what California does is usually soon followed by other states.

There are no DPFs for retrofit commercially available for small diesels, at least not yet.

Cummins can route its APU through the main Cummins engine DPF because the manufacturer designed and certified them to work together. But it’s illegal for anyone other than those authorized by the factory to tap into an exhaust system certified to 2007 standards.

And, even though pre-2007 truck engines won’t have to be retrofitted with exhaust treatment, California will require pre-2007 APUs and generators to meet standards that require DPFs.

These technical difficulties led to the growth of hybrid climate control units. They use fuel-fired heaters – Espar has three models certified for California – coupled with deep-cycle batteries powering electric air conditioners. If you build such a unit, use a battery isolator because deep-cycle batteries charge at different rates than starting batteries.

As for you not being able to afford a brand-name idle reduction product, even the most expensive units have a payback under two years; some, as short as nine months.

With a savings of more than $100 a week in fuel alone, it may be worthwhile to get a short-term loan or a lease-purchase plan. Payments come out of savings. There are also government grant and assistance programs available. See more on Page 88 of this special section.

Paul Abelson may be reached at

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