Recharged My A/C!

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Aug 30, 2004
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For the last few years, the 96 Saturn's A/C has been so-so in warm weather. About a year ago, I decided to try recharging the A/C in hopes of making it blow colder. So I bought one of those DIY A/C recharge kits by Interdynamics. It was a 19oz can of refrigerant, oil and leak-sealer with a built-in hose. I added about 1/3 of the can (5-6 ounces) and the low-pressure reading only increased by 1 psi. The air conditioning did work a bit better, but not much. I decided that it wasn't worth the risk. Last week, it was getting a bit hot. Frustrated, I called my mechanic and asked him if I could use his A/C machine. I gave him $40 in cash, and he allowed me to use his machine for an hour. Here's what I did: 1. Evacuated the system. I recovered 1.06 lbs of R-134A. If you do not count the 5-6 ounces that I added last year, my system lost about 50% of its charge (12 ounces) over the course of 14 years. 2. Vacuumed the system for 15 minutes to remove any moisture. The system had never been opened before, so I didn't think I would have any moisture. However, I did the vacuum just to be safe-- it can't hurt. I was able to draw a vacuum to -25+ degrees. 3. Charged the system with 1.5 pounds of R-134A. 4. Equalized the pressure in the hoses. On a SPX/RobinAir machine, this means that you start the car and tell the machine to allow the A/C system to suck out any refrigerant left in the A/C machine's lines. This allows for a maximum charge as sometimes there is a lot of refrigerant left in the lines of the machine. Did I do this correctly? After this was all done, I used an infrared thermometer to measure the outlet temperature. On a humid 80F day, the vent temperature was showing between 29-31F with the fan on 4 (max) and the system set to recirculate. I was also stuck in traffic yesterday and the outside temperature was 105F. With the system set to recirculate and the fan speed set to 4, the air was still fairly cold. In conclusion, I think having your system recharged with an A/C machine is the ONLY correct way to achieve maximum A/C performance. Without the machine, you cannot charge your system with the correct (or ideal) amount of refrigerant. I highly recommend that anyone who is not satisfied with their A/C system's performance to take their car into a shop to have the system professionally recharged. I think you'll be very satisfied with the results.
 
Joined
Feb 21, 2003
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Houston, Tex
 Originally Posted By: The Critic
2. Vacuumed the system for 15 minutes to remove any moisture. The system had never been opened before, so I didn't think I would have any moisture. However, I did the vacuum just to be safe-- it can't hurt. I was able to draw a vacuum to -25+ degrees.
If you have lost freon, then by definition you have replaced it with moisture laden air. Therefore it would have been better to put the system into a deep vacuum (approx. 29" of Mercury, depending on altitude, or the equivalent Micron reading) for 30+ minutes. Any vacuum is better than none, but my feeling is you didn't remove much moisture, just air. And on such an old system you should have replaced the accumulator/dryer. Again, it has absorbed a lot of moisture over the years.
 
Joined
May 7, 2004
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 Originally Posted By: The Critic
In conclusion, I think having your system recharged with an A/C machine is the ONLY correct way to achieve maximum A/C performance. Without the machine, you cannot charge your system with the correct (or ideal) amount of refrigerant.
You can use a vacuum pump to vacuum the system out. As far as measuring how much to put back in in, way back when they used to use a scale and weigh the container of Freon as the system charged. This method still works today. A scale, manifold gauge set, and a vacuum pump are all that is needed to ensure a correct charge.
 
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Jan 2, 2004
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I used the Robinair machine at work to pull a vacuum for 45 minutes, then I hooked up my el cheapo Harbor Freight gauges and refilled it at home. This was on a van, took 4 cans of refrigerant.
 
Last edited:

JHZR2

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Dec 14, 2002
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 Originally Posted By: TooManyWheels
If you have lost freon, then by definition you have replaced it with moisture laden air. Therefore it would have been better to put the system into a deep vacuum (approx. 29" of Mercury, depending on altitude, or the equivalent Micron reading) for 30+ minutes. Any vacuum is better than none, but my feeling is you didn't remove much moisture, just air. And on such an old system you should have replaced the accumulator/dryer. Again, it has absorbed a lot of moisture over the years.
Based upon what? If the charge goes below ambient pressure, then yes. If the pressure stays above ambient pressure, what driving force is there to get ambient air into the system? An AC system has liquid refrigerant in equilibrium with vapor-phase refrigerant. Depending upon the temperature, there will be less or more vapor pressure in the system. That vapor CAN leak out, but it will simply be accounted for by the liquid-phase refrigerant flashing to a vapor, to maintain pressure (just thermodynamics working). At some point, all the liquid would flash to vapor (given enough leakage for enough time), and then the vapor pressure in the system would start to decrease, as the refrigerant leaked further. At some point the pressure would be equal to ambient, and then diffusion and expansion/contraction through the leakpoint may cause an introduction of ambient air. Until then, no.
 

Kestas

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I think Critic did an excellent job with putting the system back in working order. He probably could have just topped off the refrigerant and called it good, but he though it was too risky. That's why a set of manifold gauges is a good investment for the tool box.
 
Joined
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Just so others reading this knows,you don't need a machine yes it sure would be nice but a good vac pump/gauges/scale is all you need to do a proper job,weighing your cans or 30lb cyl on a scale you can get the factory amount in no problem. just takes <u>knowledge</u>..of the in's and out's and patients been doing my own AC work for many many years.
 
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Bad Axe, MI
 Originally Posted By: brianl703
You don't need knowledge when you have a fancy machine doing all the thinking for you.
Ah, yes you do...
 
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I've read the manual that comes with that machine. I think I could train a 6th grader to handle it, which incidentally, was about the level that the manual was written at.
 
Joined
Sep 23, 2006
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 Originally Posted By: brianl703
I've read the manual that comes with that machine. I think I could train a 6th grader to handle it, which incidentally, was about the level that the manual was written at.
Thats good never know who's going to be using it!
 
Joined
Sep 23, 2004
Messages
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il
 Originally Posted By: brianl703
 Originally Posted By: The Critic
In conclusion, I think having your system recharged with an A/C machine is the ONLY correct way to achieve maximum A/C performance. Without the machine, you cannot charge your system with the correct (or ideal) amount of refrigerant.
You can use a vacuum pump to vacuum the system out. As far as measuring how much to put back in in, way back when they used to use a scale and weigh the container of Freon as the system charged. This method still works today. A scale, manifold gauge set, and a vacuum pump are all that is needed to ensure a correct charge.
What kind of vacuum pump?
 
Joined
Sep 23, 2006
Messages
11,268
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Bad Axe, MI
 Originally Posted By: JakeR22
What kind of vacuum pump?
A motor operated vain pump one like this,i have one like that but a JB 7cfm dual stage pump,she can pull a vacuum!,don't get one of those air operated ones there junk run off shop air(uses ALLOT of air)and don't pull a good vacuum.
 
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