Moparts Tech Archive

Tech Misc. Info

Converting from R12 to R134A

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.
Thanks,
Frank
============================================

WES HUTCHINSON
Moparts Member
Posts: 209
From: PUYALLUP,WA USA
Registered: Feb 2002
posted 07-02-2002 01:59 PM

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.
By the way I have done this on three different vehicles, A ford pickup, a ford car and a honda, the pickup four years ago the cars 3 years ago...still blowing cold.
Some people would say I am cheap,lazy or stupid for converting the way I did but until I have a failure I am gonna keep doing it the same way.
wes
============================================

Mike P
Moparts Member
Posts: 886
From: Stillwater, ny, usa
Registered: Aug 2001
posted 07-02-2002 02:19 PM

Ditto's to WES H. 6 for 6 on conversions.
Do a search in moparts, there is a ton of information
============================================

rt3406pak
Moparts Member
Posts: 737
From: Ft. Wayne, Indiana, USA
Registered: Nov 1999
posted 07-02-2002 02:38 PM

Try your local parts store. Conversion kits should run $34.99 and have everything except a vacuum pump.
===========================================

ViperDave
Moparts Member
Posts: 297
From: Wolcott, CT
Registered: Jul 2001
posted 07-02-2002 03:21 PM

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.
DAVE
============================================

Fairly Strange
Moparts Member
Posts: 1850
From: Gardendale, AL.USA
Registered: Nov 1999
posted 07-02-2002 06:41 PM

3 for 3, direct infusion.
No problems in 2 years.

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!
===========================================

Faust
Moparts Member
Posts: 1051
From: N. Attleboro, MA, USA
Registered: Dec 1999
posted 07-02-2002 08:42 PM

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.
============================================

bayer boys
Moparts Member
Posts: 558
From: douglasville,GA USA
Registered: Oct 2000
posted 07-02-2002 08:49 PM

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
============================================

rrsbdh
Moparts Member
Posts: 301
From: Decatur Alabama
Registered: Oct 2001
posted 07-02-2002 09:38 PM

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.
===========================================

Spanky
New Member
Posts: 38
From: Columbus, OH
Registered: May 2002
posted 07-02-2002 09:58 PM

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.
The problem is that R-134a needs to cycle at a different pressure than R-12. When the 134a is cycled at that pressure, your evaporator core may freeze up. Maybe not; depends on how humid the air is. What'd be really great is if some vendor somewhere would make an EPR valve that is calibrated for 134a... Hey! Any vendors reading this?!

BTW, the Dart worked great & was usually about 38 degrees at the vents & never froze up. Great system.
============================================

340_6Pak_Cuda
Moparts Member
Posts: 2045
From: Maryland
Registered: Nov 2001
posted 07-02-2002 10:16 PM

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.
The only mods I do to them is change the hi and low fittings.
===========================================

drbill
Moparts Member
Posts: 552
From: Detroit ,Mi,usa
Registered: Feb 2001
posted 07-02-2002 10:23 PM

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.
==========================================

72roadrunner
Moparts Member
Posts: 210
From: conowingo, Md USA
Registered: Aug 2000
posted 08-04-2002 09:17 AM

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?
============================================

fast71
Moparts Member
Posts: 884
From: Old town,fl,usa
Registered: Oct 2001
posted 08-04-2002 10:01 AM

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.
============================================

CUDANUT
New Member
Posts: 60
From: GRAYSVILLE, AL
Registered: Mar 2002
posted 08-04-2002 10:44 AM

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:
1. Flush the system
2. Change the drier, o-rings, hoses if leaking. (Most older hoses are)
3. Use ester oil for replacement oil.
4. Vaccumn the system
5. Charge with 80-85% ratio R134a.
Having said all this here is some other info. On big trucks and heavy equipment we usually change the compressor and condenser due to the addional "heat load" they carry. On cars we usually retain the compressor if it is otherwise good. We did convert about 20 older patrol units with R-134A by just evacuating the system, adding ester oil, and charging with 134A. The results were mixed. Overall the failure rate of components were higher (3 compressor failures) while the ones we did a complete conversion fared better. The ones we changed everything on did get slightly better outlet temps. We use adjustable cycling switches so we can tweak the low side pressures to get the evaporator temps as close to freeze up as practical. The moral of this story is if you are on a budget just evacuate, add oil and charge. Then if the compressor croaks change everything then. Sorry to be so long winded, I just completed a report for my boss on this very subject at work. Again, there will be many opinions on this subject, I can only relate what I have learned thru practice.
=============================================

FuryIII
Moparts Member
Posts: 122
From: Douglass, Texas, USA
Registered: Jul 2002
posted 08-04-2002 11:43 AM

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.
============================================

karfixer
Moparts Member
Posts: 1032
From: Simi Valley, The People's Republic of California
Registered: Feb 2001
posted 08-04-2002 11:53 AM

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.
============================================

5thAve
Moparts Member
Posts: 3024
From:
Registered: Jun 2000
posted 08-04-2002 12:10 PM

Yep, CUDANUT described it all perfectly!
=============================================

CUDANUT
New Member
Posts: 60
From: GRAYSVILLE, AL
Registered: Mar 2002
posted 08-04-2002 12:13 PM

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.
============================================

Swampwing
Moparts Member
Posts: 668
From: State of Denial, USA
Registered: Jan 2001
posted 08-04-2002 01:18 PM

Is an STV the same thing that Chrysler calls the EPR valve on the v2 (r2) compressors?? Seems like it.
============================================

CUDANUT
New Member
Posts: 60
From: GRAYSVILLE, AL
Registered: Mar 2002
posted 08-04-2002 01:27 PM

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.
============================================

MRMOPAR
Moparts Member
Posts: 1265
From: Tucson, AZ
Registered: Jan 2000
posted 08-04-2002 02:17 PM

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..
http://www.autofrost.com/
http://www.aircondition.com./
http://www.epa.gov/ozone/snap/refrigerants/lists/mvacs.html
=============================================

72roadrunner
Moparts Member
Posts: 210
From: conowingo, Md USA
Registered: Aug 2000
posted 08-05-2002 07:51 PM

Which do you think would be better, add more r12, add frost12 or Go ahead and switch to a134
===========================================

Michael
Moparts Member
Posts: 2833
From: Bridgeport,WV USA
Registered: Nov 1999
posted 08-05-2002 08:18 PM

--R12 if possible--
=============================================

MRMOPAR
Moparts Member
Posts: 1265
From: Tucson, AZ
Registered: Jan 2000
posted 08-05-2002 11:23 PM

I would personally go with the drop in replacements for R12. Autofrost etc.
============================================

ted
Moparts Member
Posts: 4610
From: Albany NY
Registered: Nov 1999
posted 08-05-2002 11:32 PM

i used freeze 12 in my 73 dart, works well , no problems
============================================
fgriesser
Moparts Member
Posts: 197
From: USA, Alabama
Registered: Dec 2001
posted 08-06-2002 12:49 AM

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
Frank
===========================================

BeeBody
New Member
Posts: 26
From: Tempe, AZ
Registered: Apr 2002
posted 08-06-2002 04:14 AM
I'd definately go with one of the drop-in replacements available. I personally have used the DuraCool 12a replacement in my '69 Coronet 500 with excellent results. Nothing to change except a bad hose, and the system blows COLD. Also, since you use less of the replacement coolant than you would R-12, head pressure is lower in the compressor - a lot more friendly to the system! Also, there are NO ozone layer contaminants in it - it is nice to the environment.
OOPS - I'm starting to sound like an ad for the stuff
============================================

ChargedDust
Moparts Member
Posts: 1103
From: Valley Stream, NY
Registered: Dec 1999
posted 08-04-2002 07:21 PM

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.
============================================

RKKevilly
Moparts Member
Posts: 1215
From: Bonifay, FL USA
Registered: Nov 2001
posted 08-04-2002 07:33 PM

That is very repectable IMHO. Mine runs about 58 to 60 on hot days like you are describing, on an 86 Ramcharger.
============================================

Thunderstruck
Moparts Member
Posts: 837
From: Killeen, Texas, by God!
Registered: Aug 2000
posted 08-04-2002 07:37 PM

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.
Both tested at idle, MAX ac, low fan speed. Sitting next to each other, with a digital termometer, high 90's daytimem mid 70's humidity.

Fan speed will change your outlet temps, low speed is colder.
===========================================

John Kunkel
Moparts Member
Posts: 2350
From: Rio Linda, CA, USA
Registered: Nov 1999
posted 08-04-2002 07:39 PM

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.
R134 SUX!!! (IMHO)
============================================

FuryIII
New Member
Posts: 96
From: Douglass, Texas, USA
Registered: Jul 2002
posted 08-04-2002 07:45 PM

mine will blow out 40 degree air after running 5 minutes and the temp at start was 112 inside the car.
i didnt retrofit my ac at all. just vacumed the working system and charged it with r409.
that was 6 years ago.
==========================================

moparsupremist
Moparts Member
Posts: 518
From: sac,ca
Registered: Feb 2000
posted 08-04-2002 07:47 PM

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.
=============================================

rrsbdh
Moparts Member
Posts: 625
From: Decatur Alabama
Registered: Oct 2001
posted 08-04-2002 07:54 PM

You need another can in there. I had the same thing on one of my 5th Avenue's.
============================================

Don Oremus
New Member
Posts: 51
From: Wisconsin
Registered: Apr 2002
posted 08-04-2002 08:00 PM

hello all
I just finished getting my AC together on my 69 Superbee. It has a Classic Auto Air kit for R-134A, and blows well into the 40s. I also install a 96-99 Caravan condenser so that helps. I heard that 134 is more effecient than R-12, but I am not a licensed ac technician. Happy with my AC, ready for the Nats.

Don
=============================================

ChargedDust
Moparts Member
Posts: 1103
From: Valley Stream, NY
Registered: Dec 1999
posted 08-04-2002 08:09 PM

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.
=============================================

440 Scamp
Moparts Member
Posts: 582
From: Kirkwod,Illinois
Registered: Oct 2000
posted 08-04-2002 10:12 PM

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.
============================================

Thunderstruck
Moparts Member
Posts: 837
From: Killeen, Texas, by God!
Registered: Aug 2000
posted 08-04-2002 10:24 PM

Actually, you can get R134 legally in most of the US. Certain jurisdictions/cities have banned the sale of R134 to unlicensed people.
I just took the certification a couple of months ago and that question was on the test.

Check out www.imacs.org

Steve
============================================

Jnerotten
New Member
Posts: 64
From: Norfolk, VA
Registered: Jun 2002
posted 08-04-2002 11:31 PM

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?
============================================

Brian
Moparts Member
Posts: 1229
From: Houston, Texas
Registered: Nov 1999
posted 08-04-2002 11:37 PM

The RV2 compression with R12 in my Duster blows at 45 degress.
============================================

waveraider!
Moparts Member
Posts: 699
From: Indianapolis
Registered: May 2001
posted 08-04-2002 11:47 PM

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?
============================================

Jnerotten
New Member
Posts: 64
From: Norfolk, VA
Registered: Jun 2002
posted 08-05-2002 12:03 AM

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.
=============================================

moparsupremist
Moparts Member
Posts: 518
From: sac,ca
Registered: Feb 2000
posted 08-05-2002 02:34 AM

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.
============================================

rvoyles
Moparts Member
Posts: 1604
From: Bakersfield, CA.
Registered: Aug 2000
posted 08-05-2002 03:38 AM

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.
============================================

DAVE
Moparts Member
Posts: 397
From: FT LAUD, FL
Registered: Jun 2001
posted 08-05-2002 04:21 AM

Fury whats R409?
BTW Jenerotten....I think something just rolled under your seat...
=============================================

karfixer
Moparts Member
Posts: 1028
From: Simi Valley, The People's Republic of California
Registered: Feb 2001
posted 08-05-2002 10:41 AM

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.
=============================================

dhaan
Moparts Member
Posts: 272
From: champaign, il usa
Registered: Feb 2002
posted 08-05-2002 11:22 AM

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?
dave
===========================================

Tech Index