Jon has pointed out what is currently being done on many mission critical systems for military and commercial aircraft applications. While it would be nice to have real time data with air conditioning logging on the bus, it probably would become data overload for the majority of users. Just look at the Pro Driver on you coach; it does virtually the same thing but is dedicated to the engine and makes adjustments or shuts down the engine for you.

Gulfstream aircraft systems currently in use monitor critical and non-critical system data and will send an automatic signal to the closest MRO or maintenance repair organization recommending adjustments, repairs or replacement of components. Gulfstream even goes as far as dispatching the required part before the aircraft has landed. Prevost would love this but you might not.

In the bus world only a little data needs to be collected to predict with a high degree of probability that a failure or problem will soon occur. Using the example Jon pointed out; taking differential temperature across the intake and supply ducts will give you an idea of system performance. Adding a few more readings will give you additional predictive data. Once you know the typical differential temperatures you will be able to see a trend indicating on going performance to be used as a base line. Just because the delta is increasing doesn’t mean you have more cooling capacity. The likely problem is a dirty evaporator air filter reducing the air flow etc.

In addition to Jon’s recommendation to look at the liquid receiver to see the refrigerant level on the sight glass, use your infrared thermometer to record the refrigerant temperature in the receiver. It will change with the ambient temperature but the delta between the OAT and the refrigerant should stay roughly the same. If the delta increases, there is a high probability that you have a dirty condenser coil etc.