Quote:
Originally Posted by 88911coupe
Ken and Neil...you're basically asking what I'm asking. It sounds like there's no harm in leaving my old hoses in place even if I switch to R134...
|
According to testing done by the Scientists at DuPont laboratory, and supportrf by statements from the EPA and SAE, your legacy hoses have been permeated by the lubricant used with the old R-12 refrigerant and as such will not leak the R-134a refrigerant.
But.
The factory Porsche design has failure modes, relatively common failure modes, that become of greater concern with R-134a than was with R12. That's because R-134a operates, typically, at higher condensor pressure levels, ~450 PSI, vs R-12.
The most common failure, by a large measure, is the thermostatic switch used to control the cycling of the compressor. This device has been noted to have at least 3 failure modes.
1.) Contacts "welded" together due to millions of inductive "kick" electrical arcing over the working life of the switch.
2.) Loss of the gas pressure within the capillary sensing tube resulting in improper adjustment to attain cooling, basically an "over-ride" of the capillary gas function.
3.) Misguided or inadvertent maladjustment of the capilary tube in an effort, typically, to attain a higher cooling level.
Any one of those would likely result in over-pressurization of your legacy hoses.
So along with the conversion to R-134a the installation of a binary, hi/lo, pressure switch to control (over-ride the thermostatic switch as/when needed) and protect the compressor. (prevent the compressor from operating if the refrigerant charge is to low.) is required by the EPA, and recommended by ALL.
My recommendation is to go ahead and install a trinary pressure switch.