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#1
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Cannot reach A/C high/low pressures
This is a 1990 Geo Metro. This car was previously converted to R134a.
Recently I replaced the compressor and dryer. I did everything by the book. I flushed the system with isopropyl alcohol, replaced o-rings, evacuated, oiled it and held a vacuum for several hours. There were no leaks. I even purged it again with dry N2 and evacuated again. Book calls for 1.1 lb of refrigirent (this was for R-12, so I was ready to use only 1 lb of R134a). After putting in 1 lb of R134a, the pressure did not reach the specified values (200/25 psi on the high/low sides). I added some extra refrigirent, and then some more. The pressure was still low. I ended up putting in twice the required amount of refrigirent. But the pressure was still only 125/25 psi. I do not hear or see any obvious signs leaks. Even if there were a leak, wouldn't the pressure initially go up and then slowly come down? Where is all the extra refrigerent going? The air is blowing a little cool, but nowhere near where it should be. The high side tubes are hot, which is a good sign. The compressor is turning over fine, and there are not funny sounds. I am at a loss what to try next. Any suggestions are appreciated. |
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#2
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> wrote in message ups.com... > This is a 1990 Geo Metro. This car was previously converted to R134a. > Recently I replaced the compressor and dryer. I did everything by the > book. I flushed the system with isopropyl alcohol, replaced o-rings, > evacuated, oiled it and held a vacuum for several hours. There were no > leaks. I even purged it again with dry N2 and evacuated again. > > Book calls for 1.1 lb of refrigirent (this was for R-12, so I was ready > to use only 1 lb of R134a). After putting in 1 lb of R134a, the > pressure did not reach the specified values (200/25 psi on the high/low > sides). I added some extra refrigirent, and then some more. The > pressure was still low. I ended up putting in twice the required amount > of refrigirent. But the pressure was still only 125/25 psi. I do not > hear or see any obvious signs leaks. Even if there were a leak, > wouldn't the pressure initially go up and then slowly come down? Where > is all the extra refrigerent going? The air is blowing a little cool, > but nowhere near where it should be. The high side tubes are hot, which > is a good sign. The compressor is turning over fine, and there are not > funny sounds. I am at a loss what to try next. > > Any suggestions are appreciated. > Sounds like your compressor isn't any good. Is the needle shaking or does it hold steady? Overcharging the system would only make matters worse. Did you happen to manually turn the compressor hub before letting the clutch engage? As far as I understood, the amount of R134a compared to R12 should be less. Something like 80% was it? Putting in 1 lb R134a compared to 1.1 lbs R12 is only 90%. |
#3
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Bruce Chang wrote:
> > wrote in message > ups.com... > >>This is a 1990 Geo Metro. This car was previously converted to R134a. >>Recently I replaced the compressor and dryer. I did everything by the >>book. I flushed the system with isopropyl alcohol, replaced o-rings, >>evacuated, oiled it and held a vacuum for several hours. There were no >>leaks. I even purged it again with dry N2 and evacuated again. >> >>Book calls for 1.1 lb of refrigirent (this was for R-12, so I was ready >>to use only 1 lb of R134a). After putting in 1 lb of R134a, the >>pressure did not reach the specified values (200/25 psi on the high/low >>sides). I added some extra refrigirent, and then some more. The >>pressure was still low. I ended up putting in twice the required amount >>of refrigirent. But the pressure was still only 125/25 psi. I do not >>hear or see any obvious signs leaks. Even if there were a leak, >>wouldn't the pressure initially go up and then slowly come down? Where >>is all the extra refrigerent going? The air is blowing a little cool, >>but nowhere near where it should be. The high side tubes are hot, which >>is a good sign. The compressor is turning over fine, and there are not >>funny sounds. I am at a loss what to try next. >> >>Any suggestions are appreciated. >> > > > Sounds like your compressor isn't any good. Is the needle shaking or does > it hold steady? Overcharging the system would only make matters worse. Did > you happen to manually turn the compressor hub before letting the clutch > engage? As far as I understood, the amount of R134a compared to R12 should > be less. Something like 80% was it? Putting in 1 lb R134a compared to 1.1 > lbs R12 is only 90%. > > Could be a leak, too. THAT much 134a must be going somewhere. wws |
#4
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Yes, I manually turned the hub before letting it engage. Both pressures
appear to be steady. But I agree that the problem could be the compressor. What I am afraid I might have done is put too much oil into the compressor ports. I put about 3/4 oz of the oil into the compressor and distributed the other 2 oz into the condensor and evaporator. In any case, it does sound like the compressor has gone bad. Any chance I can dismantle and repair it? |
#5
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#6
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Yes, I did put in 2 cans and then added about good part of a third can.
So that amounts to nearly 30 ounces. I did not hear any obvious leaks. But I did hear momentary hissing from the low-side valve while I was charging. It was such a short duration I doubt it could have leaked 1 lb of freon. I checked all the connections, and I don't see any sign of oil seepage. One possibility is that a leak could be inside the evaporator. But the system held a 30" vacuum for nearly 6 hours with no drop at all. I would be surprised if there is a leak. Unfortunately the compressor does not have warranty. It only had a 90-day warranty, and I kept it for almost a year before installing it. If I can't fix the compressor myself, I will have to trash it and buy another one. Is there a way to check the compressor operation without charging with freon? |
#7
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#9
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Bruce Chang wrote: > I'm pretty sure you already know this but you're using R134a and Freon > synonymously in your posts. It should be noted that Freon refers to R12. Dupont invented the name Freon to encompass several CFCs AFAIK. I use the word freon just like I call colored wax sticks crayons. 'Refrigerant' takes longer to type esp. when you are using the word alot! Toyota MDT in MO |
#10
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"Comboverfish" > wrote in message oups.com... > > > Bruce Chang wrote: > >> I'm pretty sure you already know this but you're using R134a and Freon >> synonymously in your posts. It should be noted that Freon refers to R12. > > Dupont invented the name Freon to encompass several CFCs AFAIK. I use > the word freon just like I call colored wax sticks crayons. > 'Refrigerant' takes longer to type esp. when you are using the word > alot! > Then I guess I should have said, "R134a is not Freon". I agree that it takes a lot longer to type refridgerant but I didn't want to perpetuate the misconception that all refridgerants can be referred to as Freon. If you're using Freon like you use the word crayon, then you should realize that crayons aren't trademarked by Crayola. A crayon IS a colored wax stick. I think you meant something like "band-aid" or "Xerox" or "Kleenex". That was my point in mentioning the use of Freon as a generic term for refridgerant when it doesn't encompass all refridgerants, in particular R134a. |
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