7/25/97. There is a suspected seal compatibility problem with Autofrost (R-406A) and Autofrost-X4 with York (automotive) compressors using Butyl rubber seals in some cases. Seals may fail (usually 30 mins to one hour) after the car is turned off, due to heat soak from the radiator bleeding into the condenser and raising pressures. Leaky heater water valves contribute to the problem since they allow heat to build up in the evaporator area, further increasing pressures. Dirt buildup in the radiator and condenser area also contributes by preventing the release of trapped heat after the engine is turned off. Neoprene seals are available which appear not to have this problem. For more info, contact Bobby Burke, ATC specialists, 1-800-622-5008, or email bburke@intersource.com. Web page: http://www.kiva.net/~bburke Autofrost (R- 406A) and Autofrost-X4 (GHG-X4) move more heat than does R-12. Cars with poorly maintained cooling (radiator) systems, may encounter radiator boilovers and overheating problems when changing to Autofrost, since more heat is transferred to the condenser, which rejects the heat into the radiator. It is a good idea to have the engine cooling system checked over when switching to Autofrost to prevent a dirty/clogged radiator or leaking heater water valve from causing A/C problems. There was a suspected seal compatibility problem with Autofrost. York, Techumseh and the old Chrysler RV2 compressors were thought to have a butyl rubber seal, however it has been discovered that these seal kits were made of Buna-N rubber. It has been known for many years that R-22 and Buna-N rubber are not compatible. Our research indicates that neoprene 70 is the best material for both compressor shaft seal kits and system O-rings. The makers of the York compressor have now started making their seal kits with Neoprene and manufacture neoprene seal kits for most other compressors on the market as well. Neoprene is the ideal rubber for both compressor seal kits and O-rings since it will work with all refrigerants including Autofrost and R-134a. There might still be "new old stock" seal kits on the shelves at local parts stores so technicians should ask before they buy them. We are currently discussing stocking and selling these seal kits and we are working on a master O-ring kit that will service most vehicles, foreign and domestic. We will make these available through Monroe Air Tech Inc. or tell you where they are available as we are constantly searching for other sources. O-rings are already available at most parts places. Four Seasons, Murray, and Everco have Neoprene and they are dark blue in color. GM has used a black neoprene for several years. These are available from GM dealers or AC Delco distributors. There are also green O-rings known as HNBR. This rubber was developed for R-134a because it was thought to have better heat characteristics. Also Ford used this material for their spring lock fittings. They even used an odd size (thicker) to try and keep these fittings from leaking. Autofrost will work fine with this rubber if it came from the OEMs, however HNBR O-rings that are purchased elsewhere are many times of cheap quality and will not fare well. For this reason we ask that you to always ask for Neoprene. [4/15/97 update: Bob Burke @ ATC Specialists now has shaft seal kits and O-ring kits available] On 86 and newer Ford models, safety pop-off valve on or near the compressor has a rubber seat. If this valve ever opens, then it might not reseal and leak. The cure is to use a GM pop-off valve instead (they use steel ball and seat?). We have also seen the Ford pop-off valves open at about 250 PSI, which is way too low. ALL BLENDS, INCLUDING AUTOFROST, MUST TO BE CHARGED AS LIQUID to prevent composition change, and possible damage resulting to the system. Autofrost/R-406A/Chill-it/R-414A cylinders contain a DIP TUBE that withdraws the product as liquid from the bottom with the cylinder UPRIGHT. DO NOT turn the cylinder upside down to get liquid!! This will give you vapor instead. Cylinders are marked with arrows to keep upright for liquid. No matter how much laboratory testing is done under simulated and elevated temperature conditions on materials compatibilities, field conditions are not always simulated properly. For instance, some material breakdown will be noted in a lab sealed tube test, at say, 300 degrees Fahrenheit. Most chemical reaction speed is determined by temperature, often decreasing by a factor of two for each 10 degrees the temperature is lowered. Failures in a sealed tube test in a lab at high temperatures often equate to 40 or 50 years or longer at normal temperatures encountered, far longer than the life of the car. Quoting from a DuPont publication materials compatibility section: "Actual refrigerant compatibility in real systems can be influenced by the operating conditions, the nature of the polymers used, compounding formulations of the polymers, and the curing or vulcanization processes used to create the polymer. Polymers should always be tested under actual operating conditions before reaching final conclusions about their suitability" [1]. Compositions close to Autofrost (R-406A) have been used in actual vehicles since August 1990. For further information on compatibility issues, contact Bob Burke, ATC Specialists, 1-800-622-5008 or MEA, 1-888-AUTOFROST [1-888- 288-6376], ask for code 10. [1] "DuPont SUVA(R) MP Refrigerant Blends: Properties, Uses, Storage and Handling, page 20, stock number H-45944-2 (5/93), DuPont Chemicals, Fluorochemicals Customer Service Center, Wilmington, DE 19898.