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  #1  
Old 07-08-2015, 02:48 PM
elijahbird7 elijahbird7 is offline
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Default 134a vs R12

Just wanted to report my personal experience with these products. When I bought my 59 convertible with factory a/c, it had already been converted to 134a. This summer we replaced all of the a/c hoses and recharged it with 134a. With the temperature probe in the a/c vent, the temperature of output has been no lower than 47 degrees. My low mileage 79 Mark V, has R12 in it, and when we recharged it, we stayed with R12. I just decided to check the output on it last Sunday with a temperature probe in the center vent. It initially went down to 40 degrees, but as it cycled, it stayed consistently at a 42 degree output. So basically a 5 degree advantage to keeping R12. It also may just be the difference in the whole system between the two cars, but just wanted to report my findings, and see if others have any input on temperatures of these Freon choices.
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Old 07-08-2015, 03:27 PM
Tbird1044 Tbird1044 is offline
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Quote:
Originally Posted by elijahbird7 View Post
Just wanted to report my personal experience with these products. When I bought my 59 convertible with factory a/c, it had already been converted to 134a. This summer we replaced all of the a/c hoses and recharged it with 134a. With the temperature probe in the a/c vent, the temperature of output has been no lower than 47 degrees. My low mileage 79 Mark V, has R12 in it, and when we recharged it, we stayed with R12. I just decided to check the output on it last Sunday with a temperature probe in the center vent. It initially went down to 40 degrees, but as it cycled, it stayed consistently at a 42 degree output. So basically a 5 degree advantage to keeping R12. It also may
just be the difference in the whole system between the two cars, but just wanted to report my findings, and see if others have any input on temperatures of these Freon choices.
Ever since 134A was introduced, there has been a lot of information regarding the conversion from R12. Typically the 134A is designed to run at a higher pressure than the R12. Unless you were checking the temperature on the same system after doing a conversion of refrigerant, it is hard to determine the exact affect of the change.
It will be interesting to see the responses from members that have made the change.
I have been told that if I change to the 134A, I should replace all of the hoses, the seals in the compressor and flush the system and use the right oil. I'll be following this tread closely.
Nyles
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  #3  
Old 07-08-2015, 04:09 PM
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jopizz jopizz is offline
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I've never tried it on a Thunderbird but I did convert our '92 Buick about five years ago and I haven't noticed any problems and it seems just as cool as the R12.

John
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Old 07-08-2015, 07:05 PM
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DKheld DKheld is offline
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Thanks for those temp readings - that will give me an idea of how my converted system is operating once finished. I'll have an R-134 condenser, new drier, hoses and compressor but stock evaporator and thermostat/orifice tube. I was hoping for a system that is so cold that when I pull up at a car show and open the door I could drop the temperature at the show by a few degrees -

Won't ever have an R-134 converted system preforming as it did with R-12. It all has to be designed for the specific freon used.

Most folks only refill an empty R-12 system with R-134 when actually there are many things that would help the air temp to be cooler.

The old style compressors are not as efficient at the newer Sanden rotary compressors.

Yes the hoses should be changed for two reasons - #1 the PAG oil needed for R-134 is corrosive to the old rubber hoses so all the rubber that gets eaten away in the hose will clog up the system. #2 the molecules are smaller in R-134 so the freon can leach out of the old hoses - thus the need for barrier hose. So that means changing all the seals in the system also to prevent them from clogging up the system when the new PAG or Ester oil eats away at them. The reason you cant use the old oil in the R-134 system is that it attaches to the R-134 molecules and is carried out of the compressor. We all know what happens when you have a compressor that runs without oil.

The thermostat orifice tube was designed to operate at temperatures consistent with R-12 so it would have to be sent off and re-calibrated/re-sized.

A new drier is needed - the old one will have residue in it that the R-134 will attach to and carry through the system making it less efficient.

And then the evaporator is designed for R-12 so it's less efficient - been a while but think the tube size is what needs to be changed.

I've converted a few. MG - yes a convertible MG with A/C. Used Freeze 12 in it. Supposed to be an R-12 replacement. Worked great for about a year until the compressor seal went bad and all the freon leaked out. I think the Freeze 12 has something in it that ate away at the seal.
A Nissan truck. Used R-134 on it. Flushed the system, replaced the drier, but left everything else stock. Worked great for about a year also but then the same thing happened - the PAG oil ate through the compressor seal.
My 96 truck with it stock/original R-134 system will freeze you out. I need to check the vent temps sometime just for comparison.

Interested to see what others have done.

Eric

(MG with A/C - my daily driver for 22 years)

Last edited by DKheld : 07-08-2015 at 07:16 PM.
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Old 07-09-2015, 12:42 AM
Tbird1044 Tbird1044 is offline
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Eric:
Great first hand information and experience on doing the conversion. It's add a lot of validity to things that I have already heard. I'm the guy that likes to try it and see how it works out. Looks like you've already done that.
Nyles
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  #6  
Old 07-09-2015, 03:34 PM
elijahbird7 elijahbird7 is offline
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When I called Concours Parts about getting a new expansion valve, that my mechanic said we needed, he said that most 134a conversions will give you around 50 degrees blowing out, so I guess we did better than that. There was an issue with the expansion valve though. The one that was in the car had two copper tubes, one for the sensor that was a circled tube mounted in front of the evaporator, and one with a fitting that attached to a line going into the evaporator. They only list an expansion valve for 1960 to 1966. He did not know if it would fit the 59, so he gave me a part number that I could use locally at any auto parts store just in case it wouldn't work, I could easily return it. When I took it to my mechanic, he said it wouldn't work, so I then called Classic Auto Air, where I got my a/c hose kit, and they said that expansion valve was an external equalized valve, and no one makes it anymore. He did say that we could use the one we had, and started to tell me how to modify the system. I told him to hold, and handed the phone to my mechanic, so he could hear it directly. The solution was to block off the fitting on the pipe to the evaporator. Seemed simple enough and it appears to be working properly.
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Old 07-13-2015, 09:39 AM
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Just for the heck of it (and I had my IR temp gun in the truck) I decided to measure the temps on my 19 year old R134 system this weekend for comparison.

With an outside air temp of 94 deg F the coldest air vent temp I observed was 44 deg. That was moving about 45 mph. It was around 52 deg when stopped in traffic. This "Cold" setting draws air in from the outside and cools it.

If I set the controls to MAX which recirculates the cabin air the air vent temp was much colder at 26 deg.

This system is so old it doesn't have a condenser mounted electric fan and just relies on the engine fan to suck enough air in much like the original Tbird design which I'm sure is why the vent temp comes up a bit in traffic or when stopped.

I'll find this thread when I finish my system and report back on the temps I have. I did cover the inside of the evaporator and outside of the ducts with Dynamat when I rebuilt it. Dynamat is mostly a sound deadening material but has a tiny bit of insulating properties. We'll see if it helps. I also deleted the opening in the duct that either lets cool air blow out because of the back pressure from the vents or pulls cabin air in to be recirculated - not sure what the theory is on that opening above the radio. The console gets hot from the exhaust running under the center of the car so the opening may have been to counter some of that heat.





Eric
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