Moparts Tech Archive
Tech Misc. Info
Converting from R12 to R134Afgriesser
From: USA, Alabama
Registered: Dec 2001
posted 07-02-2002 01:40 PM
I am converting my AC system from R12 to R134A. In order to make it work, I've been told to use a thermostat to replace the EPR (Evaporator Pressure Regulator) valve. Is this correct? Since I already have the thermostat I also need some info on how to hook it up: electrically in line with the 12V supply for the comressor, the temp. sensor in the same location as the sensor from the Expansion valve!? Since I am not that familiar with A/C systems it would be great to get some confirmation on this.
The only thing I have ever done is buy the low side fitting, the r134a,the oil and charged the system. That is if your system is empty. You should probably pull a vacume on it before hand, I didn't, You should probably change the dryer, I didn't and possibly pull and clean the accumulator,I didn't.
Ditto's to WES H. 6 for 6 on conversions.
Try your local parts store. Conversion kits should run $34.99 and have everything except a vacuum pump.
I didnt event evac the system i just put the 134a in with what was left of the 12, I of course did ask a few trusted mechanics about this and they said there really isnt anything against doing it. I refuse to pay all that money to evac the system, and convert it on a truck with 150k+ miles.
3 for 3, direct infusion.
The AC guys will tell you it can't be done like that. Personal experience...yes it can.
Don't let it scare you....the most you can lose is the cost of the conversion kit($24.97...last I checked at "Wallyworld"). So far I am, as well as a few others I see here, a bit ahead of the game!
Just had my furrin car done. I had it evacuated and a caccuum pulled for 1/2 an hour. After I put in the 134, I still got a lot of air out the high pressure port before I got vapor. I'm not happy with it. Slow start up, poor performance at idle.
try duracool,ya dont have to change anything,works with R12 oem,case is $65,get it from fox tool & supply,madisom,TN 615 8656251
Wes means yes and fairly strange is right on the money. I've done it too. Three words for you "Just Do It". You won't be sorry. Just drove one of mine yesterday in 100 heat not including heat index. Inside car 40 at the vent. Nice and cool 5th Avenue.
I put a/c in my Dart last summer & switched it to R-134a. A's are great because they don't have an EPR valve & use the thermostatic clutch cycling switch. Just find an A-body, yank it out of the air box, put it on yours, wire it up & remove the EPR. Piece of cake.
BTW, the Dart worked great & was usually about 38 degrees at the vents & never froze up. Great system.
I have converted dozens of vehicles from 12 to 134 without any problems. I pull a vaccum on the system before recharging but in most cases you can get by without it. If any part of the system has been open to the atmosphere for any length of time its a must to pull a vaccum.
Another thing to remember is that you don't put as much r134a in as r12. Can't remember if it's 10 or 20 percent less. Reason is the 134a works at a higher pressure.
My 1991 sundance air-conditioner needs recharged. Can I install the 134 conversion fittings and top off the system with 134 (without vacuuming the system) or do I need to remove all the R-12 first?
you must remove all r12,as the system will be contaminated immediately with just a few particles,also you need to change the drier as well!the drier has particles which cannot be removed by vacuum,you also must make sure that the compressor is compatible for the new freon,i have done this with my fleet of peterbilt trucks ,over the last couple years as the r12 system's break down,and the drier is a mandatory change and the compressor oil must be compatible.
You will get a zillion opinions on this topic. This is what I have learned with our fleet of vehicles (2,100). The proper way to do the conversion is:
im useing 409 in mine. the books say it wont work tho. all i did was pull a vacumme on my (working) system and replace the 12 with 409. that was 6 years ago.
I agree with Cudanut, What he wrote is consistant with my experience with dozens of auto/light truck conversions (FWD and RWD). The only system that was a total bust was an old Chevy p.u. with the STV/POA, never could get it to cool very well. My .02 worth, Steve.
Yep, CUDANUT described it all perfectly!
Steve, I agree, the real old systems with STV (suction throttling valves) are a bear to convert. We actually removed one on an older vehicle and retrofitted a clutch cycling switch. It worked fairly well but it was a lot of tinkering to get it to cool well. The reason older systems had all these complicated valves was that as rpm increased, so did flow and there was actually much more flow available than was needed, as thus, you needed STV valves and dual sensing expansion valves to control it. Cycling switches and electronics changed all that. Every vehicle is engineered different, you just have to understand that most older vehicles have the capability to cool well with R134A if you tweak the system properly.
Is an STV the same thing that Chrysler calls the EPR valve on the v2 (r2) compressors?? Seems like it.
Same basic thing, different name. EPR stands for "evaporator pressure regulation". It regulates suction flow. One function is to keep the compressor from ingesting liquid freon at higher flows.
There are other options allowing you to stay with a R12 drop in replacement (EPA SNAP certified for automotive use). Freeze 12 is one that works..
Which do you think would be better, add more r12, add frost12 or Go ahead and switch to a134
--R12 if possible--
I would personally go with the drop in replacements for R12. Autofrost etc.
i used freeze 12 in my 73 dart, works well , no problems
Just converted my system... Replaced the EPR valve with a thermostat which will control the compressor. Also changed the oil (ester), new receiver/dryer unit. Have not charged the system so far since I want to wait till everything else is working properly
Changed over the RamCharger last year. Out driving today I think the temp was 90°-92°, and I remembered that I had the thermometer thing in the glove compt. So I pop it in one of the vents and drive home. When I got home the needle was 55°-60°. Not refrigerator cold, and I don't know what it was blowing with R12 (low and leaking when I bought it) but I think 55° is repectable. Just thought I'd pass this on for the raging debate.
That is very repectable IMHO. Mine runs about 58 to 60 on hot days like you are describing, on an 86 Ramcharger.
That's kinda weak actually, the Neon (designed for R134) puts out low 40's, my 87 Diplomat (converted to R134) blows out high 40's.
Fan speed will change your outlet temps, low speed is colder.
Let the Ramcharger sit in the hot sun for a few hours with the windows closed and see how long it takes the R134 to bring the temp down to 55°-60° if it will. Not only will the vent temperature be higher than with R12 but it will take many more recirculating cycles to bring the temperature down.
mine will blow out 40 degree air after running 5 minutes and the temp at start was 112 inside the car.
Im a tech , and have my ASE in A/C and would never let a car leave the shop, unless it was under 50 degrees. Thats with it on max a/c and medium blow (suppose to actually put on low blow, but people dont leave the a/c on low) I think the average car that leaves the shop is between 44-48 degrees. Id say your car is atleast a half pound low on refrigerant.
You need another can in there. I had the same thing on one of my 5th Avenue's.
Yeah, I should have given more more detail. This was on the highway (~60 MPH) on MAX A/C with the fan on high. I charged the system up last year 12% less than full, supposedly correct for R134. But I haven't checked it this year to see if it leaked out any since it was never really "FULL". Nice to see some quantifiable numbers though, and at least I can get my hands on R134.
Actually you arent supposed to be able to get 134 unless you are licensed just like R12 but is not being enforced. I have retrofitted many cars and some work fairly well and some suck. Any duct temp between 36 and 48 will fly as far as customers go,I'm talking blower on high ,recirc,and highway speeds. Idle temps depend on condenser efficiency and compressor size and rpm.
Actually, you can get R134 legally in most of the US. Certain jurisdictions/cities have banned the sale of R134 to unlicensed people.
I thought the only place that did that was Wiscounsin? My system has prob not been servicied in 20 years and I'm sweating my balls off at stop lights. I think the leaks under the dash add to the humidity or something. Have no idea were there coming from. Either way, I want to switch over to the 13 but lets say my system had 0 pressure to release into the atmosblahblahblah ;-/. How do you get the old oil out in laymans terms?
The RV2 compression with R12 in my Duster blows at 45 degress.
I did the retrofit to my Challenger. I put in 1 can of oil and 2 cans of R134. The compressor runs, but it just doesn't blow out cold air. The evaporator line gets cool, but not cold like my other car. I didn't pull a vacuum on the system because I was told it wasn't necessary. Do I need to start over?
Thats what I'm wondering. In about two weeks, I'm putting her in a garage and seeing how I have to take everything apart to do my mods, I figured I might as well convert in the process. I'm clueless about ac systems so thinking I can 'blow' it clear with high pressure seems to easy to be true.
Waveraider, I would definately pull a vacuumn , make sure you have no leaks, and recharge. Also, change the receiver/dryer. When converting over, this is necessary, although some people have luck just changin oil and refrigerant. Me i dont wanna do the job twice and the receiver/dryer isnt very expensive, and the a/c will be more efficient.
you have to pull a vacuum first....I've done this retrofit successfully by just replacing the reciever/dryer and pulling a vacuum and charging it. Matter of fact...I did it with a $10 harbor freight vacuum pump hooked to an air compressor for 2 hours. I added the correct amount of oil (I think it was about 6-8 oz) and put one can of 134a that had stop leak in it and 2.5 more cans of 134 and all went well. Believe it or not, I got 36-38 deg vent temps on low fan setting in my 85 ford f-250 this way...whole swap with tools and all cost me just over $100. And the trucks AC hadn't worked for over 5 years before the swap.
Fury whats R409?
Unless the humidty is 90-100% mid 50's aren't good enough. Now r-134 is very sensitive to overcharging and without a charging station and gauges you will have a bear of a time getting the system to work. Evacuating the system is manditory, I've done dozens of retrofits and the only difference in performance is r-134 takes longer to cool down, but will get just as cold. A retrofit will not fix an old system and will show any weaknesses as the pressures do tend to be higher.
My clutch went bad and the compressor locked up. I took the low pressure side off and there was rust in the bottom of the hose. What does this mean?