Converting 93 to 134a
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From: White House TN.
Converting 93 to 134a
I am wondering how hard it is 2 convert over 2 134a? My 93 has finally stopped cooling after all these years and I guess I need 2 convert over. Is this something a mech. should do or can I do it myself? I know that I canot allow freon to go into the air. Are there any conversion kits that I should use specifically? My air worked at the start of warm time in March b4 we had a cold snap and I had 2 go back to heat. Thanx 4 any info.
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Last edited by Rockledge; May 25, 2007 at 07:24 AM.
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The reason the caravan didn't work, is because it has a mechanical expansion valve, which was "calibrated" for R12. R134a works off of different pressures, which the expansion valve was either open too much or too little for efficient operation.
The Ranger, on the other hand, uses an orifice tube and an electrical low pressure cut-off switch. These are pretty much compatible with R134a.
The conversion is simple. Have a shop evacuate the R12 out of the system. Install the new R134a fittings (should screw on the where the old caps were). Make sure you put the fittings on the right spots. You'll also need to add probably 4-6 ounces of PAG oil (or you can purchase the freon that has the oil already in it. Also they usually add a flourescent dye to make leaks that occur later on much easier to find).
It is good practice at this point to have someone vacuum out the system for a good 30-40 minutes before you add the oil. This is done to "boil" out any moisture that may have entered your A/C system while it was empty, but I can tell you from experience R134a is a lot more tolerant to moisture than R12 was, and I've seen many conversions done that omitted this step, and still ended up working just fine.
Next you charge up your system with R134a. Keep in mind you need less R134a, so take how much R12 it is supposed to hold, and multiply that by 75-80% and this is how much R134a you should put in.
Now for a couple conversion "myths" that you might hear:
1> "R134a will leak out of R12 A/C hoses" This is true.. kind of. Most vehicles since the late 80's have used double barrier hoses. If your A/C hoses are very stiff, with crimped on ends, then they are likely double barrier hoses, and will not leak R134a. R134a molecules are smaller than R12 molecules, and will tend to "seep" through the OLD hoses (well yes and no - more on this next)
2> "You have to completely flush the system to convert" This was believed to be the case in the early days of R134a, but as R134a became more and more popular, real life practice has proven that this isn't normally necessary. It was feared that the older mineral oil would interfere with R134a operation, which theoretically it could, but the fact is mineral oil is very heavy, and does not circulate well in a R134a system, due to smaller R134a molecules. This is why you have to add PAG oil when you convert, even if you do not flush the system. It is also actually recommended the system NOT be flushed if you do not have double barrier hoses. The mineral oil absorbs into the hoses and forms and extra layer of leak protection on the old hoses, which is dissolved if you flush the system, almost guaranteeing a leak.
3> "R134a does not work as well as R12" As Hank noticed, R134a did not work well in his caravan. The reason being R134a works better under higher pressures than R12. Hank's system was "calibrated" for lower pressure, resulting in poor R134a operation. Had he replaced the expansion valve with one calibrated for R134a, it would have probably worked out just fine.
You might notice a loss in performance after you complete the conversion. There are two "tweaks" that you can do that will improve things if this is the case. First off if you notice the compressor cycling more than it should, you might need to adjust the low pressure cut off switch. If you unplug it (usually located on the accumulator) you'll notice a small "standard head" screw in between the terminals. You can screw this in or out to adjust what pressure causes this switch to open. Usually half a turn is enough to compensate for the pressure difference of the new freon. You'll notice the high side pressure is going to be higher than R12.. and the low pressure is going to be a bit lower. On a 90degree day, pressures of 225/30 might have worked perfect with R12, but with R134a you might notice 310/15 would produce optimal results (not necessarily perfect for your vehicle, just an example). If the switch is calibrated to kick the compressor off at 20psi, then you'll need to adjust it a bit, or you'll never get it down to 15.
Now if you notice the high side pressure SPIKING way up (350+) then you have a poor performing condenser. Run a hose with cold water over the condenser while observing your pressure readings. If it drops down, then you'll need to either install a larger condenser, or increase airflow through the condenser. In the case of my old Crown Victoria (1988), I had to install an electric fan in front of it (scavenged from an old pontiac 6000). I wired it backwards so it would blow air into the condenser, and installed a relay, wired to the low pressure cut off switch so that anytime the compressor was on, so was the fan. After this modification my R134a system worked much, much better than when it was R12. I could see my own breath on 100+ degree days! I had some wicked pressures though... 350+ on the high side, 10-15 on the low side on a hot hot day, but blowing 34 degrees out the vents. In the old days people would cringe look at that high of a pressure, and I'll be honest.. it made me very nervous... but I drove it trouble free for three years that way.
Sorry for the novel, but I felt a lot of people would find this quite interesting and educational. Good luck!
The Ranger, on the other hand, uses an orifice tube and an electrical low pressure cut-off switch. These are pretty much compatible with R134a.
The conversion is simple. Have a shop evacuate the R12 out of the system. Install the new R134a fittings (should screw on the where the old caps were). Make sure you put the fittings on the right spots. You'll also need to add probably 4-6 ounces of PAG oil (or you can purchase the freon that has the oil already in it. Also they usually add a flourescent dye to make leaks that occur later on much easier to find).
It is good practice at this point to have someone vacuum out the system for a good 30-40 minutes before you add the oil. This is done to "boil" out any moisture that may have entered your A/C system while it was empty, but I can tell you from experience R134a is a lot more tolerant to moisture than R12 was, and I've seen many conversions done that omitted this step, and still ended up working just fine.
Next you charge up your system with R134a. Keep in mind you need less R134a, so take how much R12 it is supposed to hold, and multiply that by 75-80% and this is how much R134a you should put in.
Now for a couple conversion "myths" that you might hear:
1> "R134a will leak out of R12 A/C hoses" This is true.. kind of. Most vehicles since the late 80's have used double barrier hoses. If your A/C hoses are very stiff, with crimped on ends, then they are likely double barrier hoses, and will not leak R134a. R134a molecules are smaller than R12 molecules, and will tend to "seep" through the OLD hoses (well yes and no - more on this next)
2> "You have to completely flush the system to convert" This was believed to be the case in the early days of R134a, but as R134a became more and more popular, real life practice has proven that this isn't normally necessary. It was feared that the older mineral oil would interfere with R134a operation, which theoretically it could, but the fact is mineral oil is very heavy, and does not circulate well in a R134a system, due to smaller R134a molecules. This is why you have to add PAG oil when you convert, even if you do not flush the system. It is also actually recommended the system NOT be flushed if you do not have double barrier hoses. The mineral oil absorbs into the hoses and forms and extra layer of leak protection on the old hoses, which is dissolved if you flush the system, almost guaranteeing a leak.
3> "R134a does not work as well as R12" As Hank noticed, R134a did not work well in his caravan. The reason being R134a works better under higher pressures than R12. Hank's system was "calibrated" for lower pressure, resulting in poor R134a operation. Had he replaced the expansion valve with one calibrated for R134a, it would have probably worked out just fine.
You might notice a loss in performance after you complete the conversion. There are two "tweaks" that you can do that will improve things if this is the case. First off if you notice the compressor cycling more than it should, you might need to adjust the low pressure cut off switch. If you unplug it (usually located on the accumulator) you'll notice a small "standard head" screw in between the terminals. You can screw this in or out to adjust what pressure causes this switch to open. Usually half a turn is enough to compensate for the pressure difference of the new freon. You'll notice the high side pressure is going to be higher than R12.. and the low pressure is going to be a bit lower. On a 90degree day, pressures of 225/30 might have worked perfect with R12, but with R134a you might notice 310/15 would produce optimal results (not necessarily perfect for your vehicle, just an example). If the switch is calibrated to kick the compressor off at 20psi, then you'll need to adjust it a bit, or you'll never get it down to 15.
Now if you notice the high side pressure SPIKING way up (350+) then you have a poor performing condenser. Run a hose with cold water over the condenser while observing your pressure readings. If it drops down, then you'll need to either install a larger condenser, or increase airflow through the condenser. In the case of my old Crown Victoria (1988), I had to install an electric fan in front of it (scavenged from an old pontiac 6000). I wired it backwards so it would blow air into the condenser, and installed a relay, wired to the low pressure cut off switch so that anytime the compressor was on, so was the fan. After this modification my R134a system worked much, much better than when it was R12. I could see my own breath on 100+ degree days! I had some wicked pressures though... 350+ on the high side, 10-15 on the low side on a hot hot day, but blowing 34 degrees out the vents. In the old days people would cringe look at that high of a pressure, and I'll be honest.. it made me very nervous... but I drove it trouble free for three years that way.
Sorry for the novel, but I felt a lot of people would find this quite interesting and educational. Good luck!
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From: White House TN.
Thanx 4 the good read mazda ranger guy, very interesting info. I have done some checks and what I have found is that I have a switch in a fuse box under the hood, one is marked ac and is clicking on and off like it is working but my clutch on the compressor is not kicking in like it should. Now i have not checked any pressures on my ac system but I am going to when Iget time. I will keep ur novel mazdarangerguy in a safe place 4 if I nedd 2 reference any knowledge. Thank u.
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No problem... also that "switch" is the compressor relay.. if you want to test it just unplug the low pressure clutch cycling switch (should be located on or near the accumulator) and short the two terminals together... this should force the compressor to stay on all the time.
If it still clicks on and off while doing this, then it's possible you have a relay going bad or a bad connection in the fuse box... but I'd be willing to bet this isn't your case... most likely just low R134a charge. Don't leave it shorted like this for very long, as the compressor can get damaged.
Good luck
If it still clicks on and off while doing this, then it's possible you have a relay going bad or a bad connection in the fuse box... but I'd be willing to bet this isn't your case... most likely just low R134a charge. Don't leave it shorted like this for very long, as the compressor can get damaged.
Good luck
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