ACtion Magazine - January/February 2012 - (Page 26)

Refrigerant Oil: What you can’t see can warm you by Eugene Talley and Matt Dixon, Assistant Professors of Automotive Technology, SIU Carbondale, Illinois calibrated and the oil bottles emptied before we started. The unit hat superhero’s power would be best for fixing vehicles? Would it be psychic also had a recent filter change and vacuum pump oil service. clairvoyance, X-ray vision, or maybe just the patience of a saint? In the area of automotive air conditioning diagnosis, any of these would be helpful. Fantasy won’t make such powers a reality, especially the patience. Reality grounds the competent technician with a working knowledge of system operation, decent service information, and hopefully an accurate recovery/ recycling/recharging (RRR) station. Refrigerant oil charge is a fuzzy, often imprecise science. There is often much we don’t know and can’t see, and what can’t be seen, can warm you. So how would the refrigerant oil charge ever become wrong? Let’s review some of the ways: Has the system ever been opened or have any components been replaced? Has a previous collision provided a new condenser? Has a compressor ever been installed and if so, was it shipped dry or full of oil? Did the installer drain and measure what came out of the old compressor? Was the correct type and quantity of oil installed and did the measurement units get properly converted? Was the level of the recovery machine oil drain bottle observed? Was the proper service information used? Did someone install an off-the-shelf product on their own? Hopefully the point is made—our knowledge about actual refrigerant oil charge is often limited. The possible causes for A/C performance concerns include incorrect refrigerant charge, obstructed airflow, faulty fans, neglected cooling systems, blend door problems or metering valve issues. Who thinks about oil charge? If excessive oil is the cause some may say “I can rely on my trusted recovery machine to extract any extra oil during system service” but in many cases, it isn’t true. We thought it was time to experiment with excessive oil in a system to see the real-world effects on cooling performance. Our plan was to account for oil movement due to gravity by using vehicles with both a high mount and a low mount compressor. The high-mount choice was a 2003 Ford Ranger which uses an orifice tube and mechanical clutch fan. The low-mount compressor was on a 2007 Dodge Caravan with a TXV, electric cooling fans and rear air conditioning system. The recovery/recycle/charging station in use meets J2788 specifications and its gauges were checked for accuracy, its scale 26 ACTION • January / February 2012 W As expected, the low-mount compressor on the Caravan held more oil than the top-mounted unit on the Ranger. The first round of tests were performed in December and it was cold outside. The shop was between 66° F and 69° F with very low humidity. This was part of the plan—the method to our madness was the simple fact that many major underhood jobs and collision repairs happen during the winter months. The A/C system will need to be recharged and checked for proper operation after these repairs. Will the system meet minimum performance standards when the warmth of summer arrives? That was the second part of the test, conducted five months later. In May, when the weather in Southern Illinois was comfortably in the mid 80s with moderate humidity, some of the tests were repeated. Would the A/C perform properly for the customer? Let’s explain the process. Before performing the initial performance tests in cooler temperatures, we removed the compressors from both vehicles and drained any oil. We were looking to see how much oil had settled in the compressors when then had not been run for a long time. The Ranger compressor held 0.34 ounces and the Caravan held 1.0 ounce. After reinstalling the compressors we ran the systems in an “under-oiled” state. We then added the small amount of oil back into the system (0.34 ounces for the Ranger, 1 oz for the Caravan) and re-ran the performance test with the system at a “factory fill” level.

Table of Contents for the Digital Edition of ACtion Magazine - January/February 2012

ACtion Magazine - January/February 2012
Table of Contents
Outlook
Expansion Valve
Technically RELAY-ted
Under The Southern Cross
Leonard’s Law
Cooling Corner
Virtual View
News & Updates
Heating Up a Cooling Aftermarket
Refrigerant Oil: What You Can’t See Can Warm You
2011 Pioneer Award Honorees
Membershop Profile
Association News
Obituary
Quick Check
New Products & Services
Last Watch

ACtion Magazine - January/February 2012