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i researched enough to piece a system together in my s14 car but i need to charge it. as funds are low at this point in my life id like to try and charge it myself with r134. i have maybe 12 cans of r12 also but thought id use 134 instead. i see some cans have oil in them and some are just refrigerant. can anyone guide me on this? i have basic gauge and hoses for this but i dont want to screw this up. do i add 1 lb with oil in it and the remainder refrigerant?? thanks

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i researched enough to piece a system together in my s14 car but i need to charge it. as funds are low at this point in my life id like to try and charge it myself with r134. i have maybe 12 cans of r12 also but thought id use 134 instead. i see some cans have oil in them and some are just refrigerant. can anyone guide me on this? i have basic gauge and hoses for this but i dont want to screw this up. do i add 1 lb with oil in it and the remainder refrigerant?? thanks
Not sure the answer to your question, but I thought I would remind you that 134 and r12 need different hoses. R12 will eat the newer hoses made for 134. I do not know if the opposite is true. Just had to replace all the hoses on my Euro M5 that were replaced less that 18 mos ago because of that. Just thought I would mention it.

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i researched enough to piece a system together in my s14 car but i need to charge it. as funds are low at this point in my life id like to try and charge it myself with r134. i have maybe 12 cans of r12 also but thought id use 134 instead. i see some cans have oil in them and some are just refrigerant. can anyone guide me on this? i have basic gauge and hoses for this but i dont want to screw this up. do i add 1 lb with oil in it and the remainder refrigerant?? thanks
Not sure the answer to your question, but I thought I would remind you that 134 and r12 need different hoses. R12 will eat the newer hoses made for 134. I do not know if the opposite is true. Just had to replace all the hoses on my Euro M5 that were replaced less that 18 mos ago because of that. Just thought I would mention it.

thanks tim.. i did indeed make all my new hoses out of r134 compatible stuff

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Guest Anonymous

I beg to differ, I restored a 1972 e9 5 years ago and when I did the a/c I converted to a Sankyo rotary type compressor. In doing so I needed to change some hoses because of a difference in the fittings. I used barrier type hose for use with R134. I only had enough R12 for 1 shot at charging the system, it cools better so I used R12. So far so good, the system is still fully charged and it blows cold although these early BMW's would work pretty well as a greenhouse.

Good luck,

Doug

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Do you have a way to pull a vacuum on the system prior to chargiing? That's step #1. You'll want to pull a bit of vacuum to a) ensure you have removed all H2O from the system, and B) ensure there are no leaks prior to charging. If you don't, and have a compressor, Harbor Freight makes a small vacuum device that runs off your compressor. It'll take a few hours, but it does work, and is cheap. Have you changed the expansion valve to work with 134? If not, you might consider doing so, or just using R12.

After that, you'll need to add the appropriate oil - can't remember if it's PAG or not for 134, but the can should say what is compatible. 1 small can of oil, or a normal sized can of refrigerant w/oil, should be enough lubricant. Then add a scond can or so of refrigerant - I think the system takes about 26 oz, but may not be remembering correctly - again, there is a published spec for it, usually on an underhood sticker, which may not do you any good on this project!

Good luck.

David in Nashville

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I've been wondering about the R12 "freon" in my old Behr system. I'm eventually going to switch compressors and will most likely change the expansion valve and hoses to upgrade to the R134.

Here is the A/C sticker I got from Carl Nelson. Not sure if it will help.

post-8235-13667605203036_thumb.jpg

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I beg to differ, I restored a 1972 e9 5 years ago and when I did the a/c I converted to a Sankyo rotary type compressor. In doing so I needed to change some hoses because of a difference in the fittings. I used barrier type hose for use with R134. I only had enough R12 for 1 shot at charging the system, it cools better so I used R12. So far so good, the system is still fully charged and it blows cold although these early BMW's would work pretty well as a greenhouse.

Good luck,

Doug

Doug, The problem seems to be that the r134 specific hoses deteriorate with the use of r12. I had my AC system rebuilt with new everything in March 08. The system worked fine through V@V. By July, the hoses were shot. I had them replaced with r12 specific hoses and no problems since. Glad yours are holding up. Tim

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A system of your size. Unless the condenser is abnormally large, should have no more than 3oz of oil in it total (around 2oz should be OK) and I would make an educated guess of an R134 charge of no more than 2lbs. (the E30s use 1.75lbs R134) Fill it a little full (no more than 2.25lbs), run it, watch your gauges and vent temp and remove any unnecessary freon until the pressures and vent temp make you frozen. If the high reads higher than 300..... shut it down and let some out.

I suspect you're not using a $5k + A/C machine where it's easier to ADD little amounts of freon. In your case it's just easier to overfill a little then let some out as necessary. Do you have a vacuum pump to get all the air out and put the system under 30in of vacuum for more than 1 hour?? Things really work best when starting with a vacuum.

No more than 250psi on high side and the low should be around 20-30 with the compressor running. If you're system is set up for the compressor to cycle on and off I would not want to see it cycling quicker than once every 20 seconds or the system is too full.

The vent temp with a properly designed and operating system can be as low as 34 with 45 or lower being acceptable. It's best to test A/C systems when it is at least 75 degrees ambient, with 80+ being optimal. A lower ambient temp and the gauge readings should be lower.... a high side of no more than 200 if the ambient is less than 70 degrees.

Call me if you have any questions.... five one zero - five zero four - four zero four two. That's my cell and it's always on.

HTH, and I am not responsible if any of the above is not correct..... :b...

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As far as I know, one of the problems with changing to R134 is that the oil used in R12 systems is not compatible with R134 and gums up. You need to flush out the old oil before recharging with R134 and the proper lubricant. I believe this is done with R10 or R11, I forgot. I have not done this but have read about it several times.

W. B.

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thanks for all the replies and good info guys. much appreciated

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