134 Freon Question
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Instructor
Joined: Feb 2007
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From: shrewsbury Pa.
134 Freon Question
Anyone know how much 134 freon should go into a 1970 vette. I know that it calls for 4 lbs. of the original R-12. However a tech guy at a vendor that I bought some of my new A.C. parts from said 2 and a half lbs. is all that should go in when its been converted to 134. Seems a little low to me. The reason I feel its not enough, is With those 2.5 lbs. I had the A.C. shop put in there, air temp coming out of registers is 69 degrees, and this is LONG before the engine reaches normal operating temp., so its not the notorious "engine heat transfer" these things are prone to. All parts are brand new and or re-bulds freshly put on, and there are NO freeze up points at any of the systems parts.POA valve and evaporater tub does get cold so there is a flow of freon through the system.
Hoping that another pound of 134 will do the trick. HELP!!!! getting late in the A.C. season now. would like to know that it is working correctly befor the fall. Help!!!!!!!!!!!!
Hoping that another pound of 134 will do the trick. HELP!!!! getting late in the A.C. season now. would like to know that it is working correctly befor the fall. Help!!!!!!!!!!!!
Drifting
Joined: Jun 2005
Posts: 1,523
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From: grand prairie texas
Thats probably close to right maybe a little low still. What are your low and high side pressures? Are you getting the 69 degree temps at idle or cruising speed? If you are getting these temps a idle and using the standard engine driven fan that is probably the coolest temp you will get. The R-134 conversion runs at much higher operating temps and you need to move more air across the condensor. Try measuring your register temps with your garden hose cooling the condensor and let us know if they come down
Thread Starter
Instructor
Joined: Feb 2007
Posts: 190
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From: shrewsbury Pa.
Thats probably close to right maybe a little low still. What are your low and high side pressures? Are you getting the 69 degree temps at idle or cruising speed? If you are getting these temps a idle and using the standard engine driven fan that is probably the coolest temp you will get. The R-134 conversion runs at much higher operating temps and you need to move more air across the condensor. Try measuring your register temps with your garden hose cooling the condensor and let us know if they come down
Le Mans Master
Joined: Jul 2005
Posts: 5,752
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From: Austin Texas
The rule of thumb is when you have the correct amount of freon in a system, both the inlet and outlet tubes of the evaporator will be the same temperature. On R-12 to R-134 conversions that I do, we routinely see outlet duct temps in the high 30* range.
Drifting
Joined: Jun 2005
Posts: 1,523
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From: grand prairie texas
Squirrelguy when you check out your system tomorrow let us know what your high and low side pressures are and also what is the outside temp. Chsck these presures before you cool down the condensor because when you drop the temp on your condensor it will also drop your pressures. Like green73 said you may have to go with an electric fan. You may also find out that the R-134 refrigerant might not work for your car and have to go to another alternative refrigerant or bite the bullet and go back with R-12 providing you have no leaks in the system. Older cars just dont like the R-134
Thread Starter
Instructor
Joined: Feb 2007
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From: shrewsbury Pa.
will also check these temps tomorrow. thanks.
Thread Starter
Instructor
Joined: Feb 2007
Posts: 190
Likes: 0
From: shrewsbury Pa.
Squirrelguy when you check out your system tomorrow let us know what your high and low side pressures are and also what is the outside temp. Chsck these presures before you cool down the condensor because when you drop the temp on your condensor it will also drop your pressures. Like green73 said you may have to go with an electric fan. You may also find out that the R-134 refrigerant might not work for your car and have to go to another alternative refrigerant or bite the bullet and go back with R-12 providing you have no leaks in the system. Older cars just dont like the R-134
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Thread Starter
Instructor
Joined: Feb 2007
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From: shrewsbury Pa.
Melting Slicks
Joined: Jan 2003
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From: Doha
St. Jude Donor '08
I just rebuilt my A/C in the '71 and converted it to R134. The rule of thumb here is to charge it with R134 upto its 75% of what its supposed to be charged with R12, thats because R134 runs in a higher pressure than R12. In my case, I just charged with R134 till I got a low pressure reading of 50 and high of 260, at that point I could feel the vent air is cool and nice. I could go for more, as I have been told that with R134 I can go upto 280 on high side, but I'd rather be safe than to have a cooler temp.
BTW, did you change the oil to a R134 compatible one? I didnt when I put R134 and my compressor almost siezed! You need to flush the whole thing very well to remove any sign of the meniral oil and then put a R134 compatible along with a suitable O rings before charging it with R134.
BTW, did you change the oil to a R134 compatible one? I didnt when I put R134 and my compressor almost siezed! You need to flush the whole thing very well to remove any sign of the meniral oil and then put a R134 compatible along with a suitable O rings before charging it with R134.
Thread Starter
Instructor
Joined: Feb 2007
Posts: 190
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From: shrewsbury Pa.
I just rebuilt my A/C in the '71 and converted it to R134. The rule of thumb here is to charge it with R134 upto its 75% of what its supposed to be charged with R12, thats because R134 runs in a higher pressure than R12. In my case, I just charged with R134 till I got a low pressure reading of 50 and high of 260, at that point I could feel the vent air is cool and nice. I could go for more, as I have been told that with R134 I can go upto 280 on high side, but I'd rather be safe than to have a cooler temp.
BTW, did you change the oil to a R134 compatible one? I didnt when I put R134 and my compressor almost siezed! You need to flush the whole thing very well to remove any sign of the meniral oil and then put a R134 compatible along with a suitable O rings before charging it with R134.
BTW, did you change the oil to a R134 compatible one? I didnt when I put R134 and my compressor almost siezed! You need to flush the whole thing very well to remove any sign of the meniral oil and then put a R134 compatible along with a suitable O rings before charging it with R134.
Melting Slicks
Joined: Jan 2003
Posts: 2,877
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From: Doha
St. Jude Donor '08
Drifting
Joined: Feb 2005
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From: Richardson Tx.
Are these on Corvettes or on other cars?
Melting Slicks
Joined: Jan 2003
Posts: 2,877
Likes: 13
From: Doha
St. Jude Donor '08
Another way to know how much you need is to have a high pressure side equals to 2.2 - 2.5 times your ambient temp. i.e. if you are in a 100F ambient, then the high side shoul be between 220-250 psi.
Thread Starter
Instructor
Joined: Feb 2007
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From: shrewsbury Pa.
O.K.guys, Took a major step back today. The less than 30 day old re-manufactured compressor, just seized up!!!!! About to just rip the whole thing out and cut my losses. I'm sure I can get a refund on the compreesor, however I just ate the$189.95 it cost me to have the system evacuated,charged and filled with dye for a leak check. Dam, just shoot me now!
Pro
Joined: Jul 2005
Posts: 720
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From: Holtwood PA
O.K.guys, Took a major step back today. The less than 30 day old re-manufactured compressor, just seized up!!!!! About to just rip the whole thing out and cut my losses. I'm sure I can get a refund on the compreesor, however I just ate the$189.95 it cost me to have the system evacuated,charged and filled with dye for a leak check. Dam, just shoot me now!
Drifting
Joined: Jun 2005
Posts: 1,523
Likes: 1
From: grand prairie texas
Sorry to hear about your compressor. Prior to all the work you had done was the system operating or was there a problem that required the complete overhaul? The reason I am asking is if the mechanic that did all the work failed to flush out your system properly and some trash or metal from the system was not flushed out properly you may have a reason to go back to the shop that did the work and maybe they will make good on the recharging of the system