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The first 'hands on' test with R-152a as a retrofit refrigerant
Thanks to Chevy Bob ( we're pleased to bring you details of an informal test that compares R-12, R-134a and R-152a refrigerants in automotive A/C systems. Although we call it informal, please do not confuse that with careless. ChevyBob took all the right steps to assure his 'hands-on' test compared three almost identical A/C systems on the same day and at the same time. It's only informal because it didn't occur under 'controlled labratory conditions'. We truly thank ChevyBob for all of his efforts and time to get to the bottom of many unanswered questions. You can read more details and post questions and/or comments on the A/C help and discussion board at the COOL ZONE.

Why R-152a?
R-134a, the current automotive refrigerant has been met with several challenges ever since it became mainstream in the mid 1990's. It was never as efficient as R-12 and it posed several other evnironmental concerns (although ozone depletion is not one of them). R-152a had been 'tossed around' as a possible replacement for R-134a as the preferred automotive refrigerant. Understanding that, ChevyBob jumped into action and put his 'stable' of Cadillac's to work to complete this comparison test.

Although the test was not conducted under strictly controlled conditions, we feel the information and results will provide you an excellent insight into this new refrigerant. The test was conducted using three Cadillac's (model years 1987, 1988 and 1989). The A/C systems on these vehicles are factory C.C.O.T. (Cycling Clutch Orifice Tube) systems and are almost identical to each other; in fact, most component parts are interchangeable. The tests were conducted on the same day (May 7, 2005) utilizing three different refrigerants, all at the same time. Ambient air temperature recorded was 81ºF (27ºC); Relative humidity of 30%. You may be suprised at the results!

The 'stable' of almost identical Cadillacs for the test
Here's a look at the three test vehicles; 1987, 1988 and 1989 full size Cadillac Broghams. The A/C systems on these vehicles utilize components that are virtually identical to each other and, for the most part, interchangeable.

R-12 Refrigerant in the 1987 Cadillac Brougham
The first test vehicle, 1987 Cadillac had a full charge of R-12 and ran HIGH pressures of 175 p.s.i. and LOW pressures of 28 p.s.i. As shown below, the vent temperatures were recorded at 40ºF (4ºC). Comments or questions?

R-134a Refrigerant in the 1988 Cadillac Brougham
The 1988 Cadillac was using R-134a as a refrigerant. With a full charge and operating properly, the system pressure readings were 175 p.s.i. on the HIGH side and 25 p.s.i. on the LOW side. The vent temperatures were recorded at 47ºF (8ºC). Comments or questions?

R-152a Refrigerant in the 1989 Cadillac Brougham
The 1989 Cadillac was charged with R-152a. This is an HFC refrigerant and is considered to be somewhat flammable. This system produced pressures of 165 p.s.i. on the HIGH side with LOW pressures of 22 p.s.i. Once operating, the vent temperatures (as shown below) were recorded at 45ºF (7ºC). Also note that this vehicle was using a FORD Blue orifice tube which has a slightly smaller opening than the original GM White tube. From the test data it's not clear if that (alone) provided the lower pressures. Comments or questions?
See how these three refrigerants stack up against each other when you put the details on a chart.

Photos and test data courtesy of chevybob
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