The Beginning:
Precise Mechanical Temperature Switches

The company was founded in 1976 as Index Industries when Richard Englund purchased and resurrected a product line of bi-metal thermal switches, which had been dormant for seven years under its previous owner. Englund, an engineer who had experience in the design and manufacturing of bi-metal thermal switches, steered the product line toward engine and vehicle applications after discovering the need for more precise control of on-off fan clutches in Class 8 trucks.

The company improved the bi-metal temp switch technology to provide the best possible specs for that application, optimizing engine temperature and fan-on time for improved fuel efficiency. Using a unique vibration-resistant "double-snap" design, Index’s line of mechanical temp switches has since grown to serve a variety of temperature control, warning, and shutdown applications.

Versatility and Customization
Through Electronics

In the early 1980s, Index developed the first engine-mounted electronic temperature switches. These solid-state switches had longer life and added features not possible with mechanical switches. One device could contain two switch outputs with separate set and reset temperatures, further optimizing performance of the customer’s product.

Reliable Pressure Switches Introduced

Index developed its pressure switches in the late 1980s as a natural offshoot of its temperature switch technology. Employing the same “double-snap” vibration resistance principle, Index pressure switches have proven themselves over millions of cycles in air conditioning, transmission, oil, and air pressure applications.

A/C Protection and Fan Timing Controls

With it’s A/C and fan switch experience, the company saw a cost-reduction opportunity for its heavy truck customers in the early 1990s. A pressure switch in the air conditioning system frequently turns on the cooling fan to reduce A/C pressure. However, an A/C fan switch operating alone can cause the fan clutch to cycle rapidly, causing premature clutch wear and tear and excessive noise. Index engineers recognized that more “intelligence” was needed in this link between the A/C system and the cooling fan, and invented the K7 Fan Control Kit. When engine cooling is needed, the temp/timer control acts as a typical fan control switch. But when triggered by the A/C pressure switch, the control runs the fan for three minutes. This greatly reduces overall A/C system pressures and fan cycling frequency, and extends system life.

The value of Index’s innovation in fan control timing was so widely recognized that A/C-triggered fan timing was incorporated into all Engine Control Modules (ECMs) when they were introduced in 1994.

APAds: Integration of Smart Controls

Inquiring further with truck fleets about their A/C system experiences, Index saw great potential to reduce high A/C maintenance costs associated with issues such as frustrating troubleshooting and frequent replacement of clutches and compressors. In 1995, following extensive testing and analysis, the company introduced APAds (Air Conditioning Protection and Diagnostic System), a “smart” control system that extends the life of many A/C system components. APAds suspends A/C operation under harmful pressure or voltage conditions, ensures regular system lubrication, and provides diagnostic fault codes that reduce troubleshooting and maintenance time. A 9-million-mile field test on over 100 trucks showed A/C maintenance costs on trucks with APAds were up to 64% lower than on trucks without the system.

Since it was introduced in the mid-1990s, more than 500,000 APAds systems have been installed on trucks in North America, either as standard equipment or as a spec option. A similar product, the AC-X10 Air Conditioning Life Extender, was introduced in late 2002. The AC-X10 offers the protection benefits of APAds (without the diagnostic features) in an easy-to-install configuration.

The Future: Smart Sensors, Distributed Controls, System Monitoring

Index continues to expand its focus on helping industrial vehicles and equipment OEMs and users add innovation and efficiency to their products. Index’s switch, sensor and controls will play a growing role “behind the scenes” improving basic machine operation, as well as benefit equipment users with easier operation, diagnostics, and lower maintenance costs.