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  #1  
Old 01-27-2003, 01:03 AM
sms sms is offline
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Join Date: Dec 2001
Location: Hartford
Posts: 134
R134a For Diagnosis Only?

Can I use r134a to determine where the a/c leak is in my 560sl and then charge with R12 later after I replace the failed components? System has no R12 in it now and I'm not sure what's wrong with it since compressor won't even kick on with no charge of freon. I think the compressor is probably shot (bad seals)! Since r134a is easy to come by, I'd use it for trouble shooting and then use my coveted supply of r12 for the final charge once I replace the receiver/drier & compressor.

Thanks,

Steve
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  #2  
Old 01-27-2003, 08:27 AM
LarryBible
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The problem with this approach is that you cannot interchange the oil used with R12, with the oil used with R134a.

This does not mean that your idea is without merit, however. If you are willing to flush the entire system and change the compressor oil after you have located your leak, then this MIGHT be a practical thing to do.

To begin with, R12 is coming down in price.

Your approach also depends upon what leak detection you have on hand or plan to use. If you plan on using UV dye and a black light, then using the 134 and flushing later may be reasonable.

If, on the other hand, you have a sniffer, you can rig up a Nitrogen bottle, put in 2 ounces of R22, then pressurize the system at about 200PSI with Nitrogen. This will put the entire system under pressure and your sniffer can detect the leak wherever it might be. This method is legal. The EPA figures that it is better to have 2ounces of R22 in the atmosphere than to have a complete charge of R12 or even R134a.

I totally understand your wanting to take whatever measures necessary to conserve your remaining R12. I am down to about six pounds myself and I hold my breath every spring hoping that my 124 evaporator hasn't sprung a leak.

Good luck,
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  #3  
Old 01-27-2003, 12:22 PM
sms sms is offline
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Join Date: Dec 2001
Location: Hartford
Posts: 134
Larry,

Thanks for your response!!! If I don't add the 134a oil, do I still need to flush. If I do need to flush the system, how do I go about doing that. I have a set of gages and a commercial vacuum pump. What else might I need?

Thanks again,

Steve
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  #4  
Old 01-27-2003, 01:47 PM
LarryBible
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Yes, because the only way you will be able to use the r134 for your diagnostic efforts is to run the system. This will mix the oil with the 134, a bad situation. The system will have to be THOROUGHLY flushed and the correct amount of mineral introduced into the system before running the R12 system.

Good luck,
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  #5  
Old 01-27-2003, 02:21 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
If you have a Merchant's Tire place nearby, they have a good deal on diagnosis - $39.95, plus a pound of R12.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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