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Extending the life of your A/C system
During the winter months, it goes completely unnoticed, but during the stifling summer heat, the truck’s air-conditioning system is your best friend

Even though your air conditioning isn’t working during the colder months, certain conditions could be setting you up for an A/C system failure in the middle of summer.

The most common culprit is refrigerant leakage. Slowly, silently, refrigerant can be escaping from the system until it reaches critically low levels.

When you turn on an air conditioner with low refrigerant levels, the system’s compressor and clutch must work a lot harder. If the level is low enough, the compressor will cycle frequently enough to overheat and eventually fail.

Refrigerant change
So why does the refrigerant leak in the first place? It’s very difficult to completely seal a system and keep it sealed, according to Gary Wilson, sales and marketing manager for Index Sensors & Controls, a manufacturer of air-conditioning monitoring and maintenance products.

“Seals will deteriorate over time, particularly if the air conditioning hasn’t been used for a number of months,” Wilson says. “If lubricant isn’t contacting the seals, they can warp and start leaking.”

Wilson says the switch to new refrigerants in recent years has not helped the situation. Prior to 1995, all A/C systems used R-12 refrigerant, also known as Freon. Today, all new vehicles use R-134a, which contains fewer chlorofluorocarbons and is more friendly to the environment.

“The arrival of R-134a brought along its own set of challenges,” says Wilson. “Since R-134a boils at a higher temperature than R-12, it’s a less efficient refrigerant. Air-conditioning systems must run higher discharge (head) pressures with R-134a. This places extra stress on A/C compressors, which must work longer under full load.

“R134a refrigerant also has smaller molecules, so it’s more difficult to prevent leaks. Hoses and seals must be high-quality, and all connections must be tight.”

Wilson also warned truck owners about changing an R-12 system to R-134a.

“The lubricant used in R-134a systems is totally incompatible with the mineral-based lubricant used for R-12,” he says. “If you choose to retrofit a pre-1995 vehicle with an R-134a system, you must make sure that all hoses are replaced and the old mineral oil used with R-12 is thoroughly flushed out of the system. If the ester-based oil contacts any mineral oil, there’s a chemical reaction which forms an acid that attacks all of the aluminum components in the A/C system.”

Early warning
Without some type of monitoring system, refrigerant leaks are difficult to detect before it’s too late. By the time you notice a drop in A/C performance, the damage may already have been done to the compressor and/or clutch.

An untimely failure of the A/C system impacts you in a couple of ways:

  1. Higher maintenance costs associated with unscheduled repairs. Anything repaired in a hurry at unplanned locations will always cost more.
  2. Unscheduled downtime and frustration.

The need for an A/C “early warning system” was identified by Stanwood, WA-based Index Sensors in the early 1990s. In talking to truck owners, Index saw the potential to reduce high A/C maintenance costs if you could buy some time before components failed.

In 1995, 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, the company says, suspends A/C operation under harmful pressure or voltage conditions, ensures regular system lubrication and provides diagnostic fault codes that are designed to reduce troubleshooting and maintenance time. A 9-million-mile field test on more than 100 trucks showed A/C maintenance costs on trucks with APAds were up to 64 percent lower than on trucks without the system.

Since it was introduced, more than 500,000 APAds systems have been installed on trucks in North America, either as standard equipment or as a spec option.

Index Sensors & Controls has developed a new system to stave off untimely A/C failures. A monitoring system plumbed into the vehicle’s A/C system, the ACX-10 Air Conditioning Life Extender protects a number of components against premature failure and allows a fleet to deal with a problem during a scheduled maintenance interval, the company says.

When it detects persistent high or low refrigerant pressure, it disengages the A/C clutch until the pressure returns to the normal, safe operating range. This prevents harmful rapid cycling of the compressor.

The system also detects big swings in voltage. Over-voltage damages an A/C system by creating excessive current and heat in the clutch oil, shortening clutch life. Under-voltage is even worse: It can cause the clutch to slip and burn out. When either of these conditions is detected, the A/C clutch is temporarily disengaged until the voltage returns to normal.

A third area of protection is the starter motor and batteries. If the A/C is on during a vehicle’s ignition cycle, the starter motor has to work extra hard cranking the compressor as well as the engine. The ACX-10 is designed to extend starter motor and battery life by delaying A/C clutch engagement for 15 seconds after ignition, removing the burden of cranking the compressor.

The ACX-10 is a solid-state module that the company says is relatively easy to retrofit. It can be installed in less than an hour in most trucks.

March/April
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