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I am scared to flush, I heard that flush stuck inside and you can't get it out you are done. I am right in the middle, scared to flush, scared to convert to R12 scared to drain. I don't know what to do |
70% you're way undercharged. Having recharged many Gen II's, the ideal weight for an empty system in our climate is 42 ounces. Factory charge is ~46 ounces. Roughly 90% of the R12 charge by weight. Lots of armchair experts like to quote hard numbers when converting "because that's what the Internet said". Most of them are also the same ones that ***** about their converted A/C being weak. Charging a converted system is more of an art than a science, you're not dealing with the factory weight of refrigerant specified by the engineers who designed it.
If you're uncomfortable going straight to 42 ounces, add in 36 ounces, park a reliable temperature probe in the center vent, fan on Max, temp wheel on min cold, all 4 doors wide open. Continue very slowly adding gas in short bursts and watching the temperature gauge in the center vent. Keep adding gas and waiting (1-2 minutes) in between additions until the center vent temperature is 30˚F below the ambient temperature (if it's 85 outside, keep adding SLOWLY until you're at 55). If you want to get the charge perfect, continue adding very short gas bursts and giving the system time to equalize between additions until you see no further reduction of temperature at the center vent. You'll find you added 41-42 ounces of 134a. Having been charging Fords, Hondas, Mercedes, BMW's, Mazdas, Mitsubishis, Chryslers, GM's, and too many others I've forgotten about over the years, I can promise if you charge the system carefully and deliberately, you'll have ice-cold air with 134a. Your head pressure will be higher than you expect it to be on a modern car. Ignore that. You're dealing with a converted system, the head pressure will be higher at a proper charge. The Denso compressor will handle it no sweat. The head pressure will actually DROP once you're moving and have air blowing through the grille and the system catches up with the heat load in the cabin. |
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Depending on the system design and BTU capacity, retrofitting to R134a from R12 will be anywhere from 70-95% of the charge weight of R12. The vast majority fall in the 80-90% range.
You can flush the system if you want. While you have it apart, replace every O-ring in the system and use Nylog (blue bottle) smeared on the O-rings. Remove the expansion valve while you have it apart, it needs to come out to flush the system anyway. After you flush, blow everything out with compressed air until nothing else comes out. When you put the system back together, pump it down on the vacuum pump for a minimum of 1 hour to make sure you have a nice dry system. Keep in mind that the dye will stain the oil residues in the compressor, so when you recharge, you'll still have some yellow dye in there. |
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If you have the same setup as the Gen I (I assume you do since the early Gen II didn't have the passenger side airbag yet) then the way to check this is by either pulling the glove compartment (easier to see)or popping out the little grey plastic oval in the back of it. Shine a flashlight in the opening. See pictures which show the open flap (lets outside air in) and closed (recycles cabin air -hence colder). The flap is the part with the deteriorating foam on it. |
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Most of the Denso compressor car take between 7.5-8.5oz of oil. 7.75 oz should be plenty. My preference is PAO68 since it has superior lubrication properties to PAG46 and is not hydroscopic, meaning that if any moisture ever enters the system it will not turn the oil acidic. |
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Lol. To be fair my '83SD did see 34°F (even below) at the vent at minimum of 45mph with outside temps of high 80's low 90's and typical FL humidity running Duracool (hydrocarbon) refrigerant. Of course in traffic/idling, as you note, it would go up to 50°F and more. Have a can of grinding rocks R4 in my new '85SD giving at best 55°F at highway speeds so it's due for a refurb. Hence my previous question. |
before and after pictures
https://ibb.co/6NpC8Cv https://ibb.co/gMz9WmH Thank you for the great information !!!! |
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