retro fit R12 to R134 Information please

wilson ind

Well-known Member
Retro fiting geo tractor to 134 refrigrant. N. APA auto supply list two flush solvents . Local store fellows do not seem to know how the flush is used. Any help here?? I have access to vaccume unit. Will vacccume pull out any flushing agents?? Sure could use advise from anybody having direct experience !!
 
I've done a lot of these conversions and you dont need to flush the system. The flush is for a component failure to clean filings out of the system. Just pick up a conversion kit at napa put on the new fittings add the new oil and recharge the system. Make sure you empty and vacuum the system before you start the retrofit. Also you dont need as much 134 as r12 dont remember off the top of my head but I think you only need 80% so take r12 x .80 = r134 needed
 
I was always told you needed to flush out the old r-12 oil, then put in the new oil for r-134 since the oils won't mix.
Then pull a vacuum for a few hours to get all the moisture out of the system.
 
I have heard it said you can just drain the old R-12 out then fill with the 134A and then others say you can not. I have seen it done both ways and both seemed to work just fine. I have done a couple and replaced the filter/dryer on one and it worked fine and on the other I did not replace it and it also worked. Can nit say which you should be just know what I have done in the past and had it work
 
Other problems than seals and oil. The molecular size of 134 is much smaller than 12 and 12 hoses can't contain it.

Mark
 
i"ll second the component failure is the only reason to flush. I"ve changed over dozens. once in awhile, I will need to change the receiver/dryer but it proly needed changing before!
 
If that is true then, can I just replace the fittings on my 4430, replace the leaky line and add 134 after pulling a vacuum for a few hours? Use the old compressor that works fine?
I suppose I am out nothing as it is right now since the line to the condensor is bad and leaks.
 
The R12 oil will not circulate propperly with r134 thats why you need the new oil but theres no need to worry about getting the old oil out. I know John Deere recomends changing compressor and lines to retrofit but I know it will work with the old compressor. Like was said may have some line leakage and have to top off once and a while. I dont know any automotive line that needs a compressor or line change to do the retrofit.
 
Hopefully I will not write too much here having had classes in the non-mobile types of A/C and have worked on various mobile systems for years. There is a stigma attached to retrofits and the oil compatibility of each. 5% mineral oil is the max recommended for a small hermetically sealed system, the rest should be an ester based oil. Having said that mobile units use PAG oil which is different. Using a recovery unit usually removes most of the oil from the system during the recovery cycle. When recharging add some PAG especially if changing the compressor.Of course if fixing a 134A system and have the refrigerant it can go back in if recovery was done correctly. Most repair stores require changing the accumulator/drier and the metering device if a standard orifice. Oil return on mobile systems does not seem to be a problem as the velocity of the refrigerant is enough to get it back to the compressor and the compressor is different than the sealed motor/ pump units that have electrical windings in them. Flushing really applies to burnt wires in the electrical motor which you do not have , so flushing isn't going to help a lot. So fix the leaks, changing the o-rings as mentioned before, vacuum for a long time if possible(500 microns if you have a gauge but mobile systems are hard to seal for that quality of vacuum) and recharge to 80% by weight or by the correct volume if using a sight glass. It should be fine, I have done quite a few over the years and they last quite a while but due to the shaking and such will eventually leak. Occasionally I run across a system that does not leak which is great. All the rest of the posts are good info also if I missed something.
 
I am an auto tech and have literally performed 100's of retrofits over the years. Here is what you need to do....
1. evacuate the system
2. pull a vacumn to "boil" off any residual moisture
3. charge retrofit oil, most kits will use ester oil as it is compatible with both R12 and R134a oil
4. charge refrigerant to 80% of the R12 capacity.

That is it.....Done. No need to flush as the R134a won't "carry" the R12 oil so it just sits in the bottom of the system, that is why you need to add retrofit oil, it is also part of the reason you only charge to 80% capacity, the old oil is taking up some of the capacity.

When we first started doing these there where a lot of myths around about having to change lines and compressors and anything else you can think of, it is just false. the only real difference in the two systems is the oil, the seals and hoses are all made of the same material.

I will however say that it would not be a bad idea to change the receiver/drier or accumulator (whichever your system uses) This part contains a dessicant to absorb moisture, If the system has been flat or open for any length of time the dessicant is most likely saturated and can no longer do it's job. This however has nothing to do with the retrofit, just a good preventative measure on a system that has been idle for a long time.
Hope this was helpful, sorry for being long winded

Kevin
 
All good replies. In our auto shop we added a high pressure cut-out switch in the system if it didn't have one already. This will keep from burning the compressor in really high pressure/hot weather. The high pressure switch was a required part of the retro back then, still a good thing where there isn't a switch already. HTH
 

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