I'm doing a conversion from R12 to R134 on a 1982 Vette.
I replaced the compressor ( new AC Delco), seals, hose assembly, and dryer.
I had the condensor checked for leaks, resealed the heater box, installed a new heater core, checked and or repaired all vacuum lines, checked all actuators for operation, including the right vent door.
I plan to evacuate the system for one hour, then see if it holds vacuum for one more hour.
My question is - What amount of oil do I put in the system ( I have Estercool oil and some Pag oil )and how many pounds of R134?
I'm just an old wrench wanting to finish a five year project. Thankx,
xfire

The rule of thumb is 2 oz per hose, 3 oz for the accumulator/dryer, 3 or 4 oz for an evaporator or condenser, depending on size.

This does vary. Partly depending on how thoroughly the system was cleaned out already. New parts are completely clean, but sometimes come with some oil. Which ones were yours?
The compressors vary a great deal. Check the mfg specs. The information that came with the compressor will usually tell you.

I know this is general stuff, but it's a starting point.

Thanks for the help Ken, I think I have the oil part figured out now, but, when I put the R134 in, do I look for the same Hi Side / Lo side readings on my gauges same as if it had R12 in the system, or, do you put in so many pounds? One kit I saw said to only put in 85% of what the system is to have in it.
The older I get, the less I know!!!


Thanks,
Denny

85% is a good starting point. Then check the performance and pressure of the system. You may or may not need a bit more.

Low side pressure will be about the same. The high side pressure could easily be 10% greater.

And with the original expansion valve, you will have about 10% less efficency. But in the small cabin of the C3, you won't notice the difference.

Thanks again Ken, for your help. I'll let you know how it turns out.
I still have lots to do on the thing, I rebuilt the motor and about everything else inside, under, over, and on top!

Denny

I'm thinking of doing a conversion on my 79. Was it expensive ? and do you really have to replace all the parts. My R12 system works but with the future demise of it....

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Lifetime Member #73

The Money Pit.... and my niece

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The answer is both yes and no.  None of the rubber parts or seals in our cars are designed to hold the R134a.  But through age and time a coating forms on the inside of the system, which provides a barrier seal.  If you don't flush the system, it will usually hold.  But a leak will require updated components anywhere it needs to disturb the coating.

 Is it worth it ?

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Lifetime Member #73

The Money Pit.... and my niece

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I'm not sure yet, I just got the motor in and started. I still have to put the A/C pump and smog junk on yet. I'll let you know how it works when I'm done.

I replaced everything, including the "o" rings for R134.

xfire

Jim, if your system is working well the answer is no, it's not worth it.

But if you need to do repairs, then yes it is worth it.  R-12 is going away.  Sooner or later we will all need to convert.

kstyer is right.My shop guy told me that unless you have to change major parts it's not worth doing it.The r134a just don't cool as well are the old stuff.

Just to add  to the thread - I did mine. Got an interdynamics kit, with all the info, etc to change it over.  Also had a good guage set for 134a.  On mine, it was a matter of drawing it down, charging it with the new oil (which is compatible with the old R-12 oil) and charging with 134a. Took 3 cans and I was good to go.

According to a licensed AC guy the only issue with the 134a swap is that the original oil for 134a was not compatible with the R12 oils and would attack the seals.  This is not supposed to be a problem with the new kits.  Napa, Pep boys, and just about any auto parts place sells the interdynamics kit for about 30-35 bucks.  So it isn't expensive.  Have used this same kit on 3 other cars with great results and have not had any problems after several AC seasons in NC.

Good Luck!

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C3: 1979 Corvette Coupe, Auto, L-48, Red/Doeskin (my wife's fave);

I still have not had time to work on the air yet, I'm still doing other things when I have time. I did make sure to seal all the air ducts and the HVAC case, did find the vent on the right side kick panel froze open and the seal bad. That would let hot air in when using the A/C, or cold air in when using the heater. Sure is a money pit, Like a boat! A boat is a hole in the water to dump money into! LOL!

You guys have a great day,

Xfire

My system is m-t, so I guess it's as good a time as any to go 134a. It gets hot and humid in STL area in the summer. I figure I'll need it.

______________

Lifetime Member #73

The Money Pit.... and my niece

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When I bought my 82 last April, the AC didn't work and had not worked for at least eight years. I took it to a local garage where they check for leaks. Checked out OK so they replaced some hoses and valves, charged it up and I was cool all summer. Cost me about a buck fifty. We'll see how long it lasts. Hope to get it out of storage by April 1.

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Ken couldn't have said it better. I've converted cars from r12 to 134a and when done properly there are no problems. The high side is up to 20% higher so a new compressor is needed. The less efficient cooling in a corvette would not be noticed. I converted my 91 Chevy 2500 Suburban with dual air a few years ago and it cools OK but not great like the new cars.  On each switch I replaced all the seals & flushed the complete system first and there was a lot of junk that came out.  So I would advise flushing the system. The sell a flush kit & it's not to much.

Alan

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I am about ready to start doing the same thing in my '78 with the "pancake" compressor. I got the compressor from Advance Auto Parts for $139.00 plus a new receiver/ dryer with orfice tube for $44.00. I haven't gotten deep into the job yet, but on the surface, I do not see the original rec./ dryer. Once I get deeper into the job, the location may become obvious, but in case it's not.... Where does the receiver/ dryer mount?

Also... what is involved in flushing the system and how does one go about it. I have converted a '67 T-Bird over several years ago with cavernous underhood space and do not recall any problems other than significantly reduced efficiency. I had all new hoses made up for that job and have aded only 1 pound of R-134 in 6 years. I am going to try this one using the existing factory hoses, then replace as necessary if they fail a leak-down test..

Dave

Look in the right wheel well behind the front wheel.

Flushing requires a pressure source and a special flush fluid.  It is just forced/sprayed through the system components.  Don't flush the compresser or dryer.  You also don't want to flush the expansion valve or orifice, depending on which on you have.  Replace an orifice valve, only a couple of bucks.  Flush the expansion valve BACKWARDS, and out of the system.  Otherwise the crud in the inlet screen will clog the system.

kstyer38434.615775463

Ken,

I guess this special fluid is available at a parts house. How much is used in the process? Is it a one-pass deal?

I might be able to use an air/oil tank or a pump-up garden spray bottle as a pressure source.

Dave

Ken,

PS: Thanks... Ida never thunk to look inside the wheel well until a hose led me there!

Dave

You will use less than a qt. Most parts supplies sell a kit for this which isnt very expensive. When you flush you'll know you got a clean start.

Good luck

Alan

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Alan,

I'm on it this weekend, hope it works. The old bomb has a few other issues.... like it won't blow air out of the dash vents. Likely has a busted mechanical linkage and I dread tearing into the console and dash. Gonna get it cold first.

Dave

Arright!!!! I pulled the car into the garage today and peered down into the right front fender well behind the wheel well looking for the accumulator/ dryer, and shore-nuff, thar she was. Looks like they built the whole car around it. I got my good ole Hayes '63-'82 Corvette manual out . It said (after disconnecting all the lines) "Loosen the mounting brackett bolts and lift the accumulator out." Sounds simple... but there is maybe 1-1/2" of room to remove a 3" dia x 10" long vessel.

Surely there's gotta be some way of getting this can replaced short of cutting the fender off, which will surely scratch my new paint. Any of you smart guys out there have any suggestions to simplify this task???

I took the vent on the fender out, that way you can remove the line from the dryer by reaching from outside the fender with your wrenches.

Take the strap off the dryer, remove the coolant tank, then you should have room to take out the dryer.

Good luck, it ain't fun, but, it's worth it!

Denny

You have to hold your tounge funny and say the right words (NO not THOSE words)

If you have a short set of wrenches, it helps.  You may need the long ones to break the lines loose.  Be sure to hold a wrench on each side of each fitting, or you could do some damage.

Well CRAP! I gotta feelin' I'm gonna use a lot of THOSE words and bite my tongue off B4 I get 'er done. Nothing resembling a vent on the '78, just a big black box on the right hand side of the firewall with hi and lo refrigerant lines going in and out that must be the evaporator, and the coolant tank in the way. Looks like it might be possible if I get the coolant tank out of the way. It has several lines in the way that gotta be removed to pull it, but once it's gone, looks like I can get in there if I put a spare universal elbow in my forearm. Hope I don't have to pull that black box. It almost looks like it is molded into the firewall!!

I guess there's no smart easy way to get it out. Looks tougher from the top than pulling the engine and tranny!!! Almost think it would be easier to just sweat a lot again this summer.

Dave

I'm not sure what your fender right behind the wheel on the outside looks like, but , can you take it out?

Denny

Denny,

Nope! Mine's a solid molded inner fender well....maybe if I pull the wheel, I could open up an access hole with a Sawzall but........ no guts. I promise... they built the car around the accumulator/dryer. What year is yours with the vent???

I put a complete after-market A/C unit on my '59 Chev Biscayne in about 4 hrs (not including the time it took to fab a compressor/alternator mounting bracket). That job looks like a piece of cake compared to what I see on this '78. Now I know why the previous owners never fixed this one. I'll keep you posted on my progress over the weekend if I can do it without using THOSE words. It may not really be THAT bad, but it sure looks that way.

BTW... I'm a kinda lazy shade-tree wrench....

Dave

Dave,

Sorry, I thought you had a hole between your wheel opening and door like mine. I have a 1982. I called it a vent, I guess it's a fender louver grill. Three screws and it's out. Sure makes it easy to unhook the line from the dryer.

Hope you don't have too much trouble.

Denny

I might just go out and trade it for an '82 on Monday!

You don't have to take any of the body apart, but it would be easier if you could.  It does not look like it,  but it will come out.

Ken,

You sound like the voice of experience. I think I was not serious about taking a sawzall to the fender. Will it come out through the void left after pulling the coolant overflow tank, or am I gonna have to remove the "black box" evaporator???

Dave

I have worked on a few.  I am an ASE Master Auto, Master Truck, and Master Paint and Body tech.  I fixed car for over 25 years, and now teach others to fix them at a tech college.  I worked for Chevrolet dealers from 77 to about 82.  So I worked on our C3s when they were new.  Granted, the problems then are not the same as we have now on 20 and 30 year old cars.  Having said all that, I must also say I learn a lot from everyone here.  Everyone here knows something about a C3 that I don't.  Some know a lot.  It's a great bunch of people.

No, you don't need to pull the evaporator housing.  It will come out from the inside top of the left fender.  The surrounding items do need to be removed.  These vary from year to year.
kstyer38436.8211458333

[QUOTE=xfire]

I still have not had time to work on the air yet, I'm still doing other things when I have time. I did make sure to seal all the air ducts and the HVAC case, did find the vent on the right side kick panel froze open and the seal bad. That would let hot air in when using the A/C, or cold air in when using the heater. Sure is a money pit, Like a boat! A boat is a hole in the water to dump money into! LOL!

You guys have a great day,

Xfire

[/QUOTE]

For what it's worth, I was able to make a new seal for the fresh air door by using a piece of rubber roofing material. Worked great and I'm sure it's going to last longer then the original foam material the general used.

I think I only paid $13.00 for the vent kit, it had the rivits with it, also, would do two vents. My 82 only has one vent, so, that means I'll have to buy another Vette!!!

 

Hey Y'all, Ken, Denny, xfire and all.....

I finally got 'er 'bout done yesterday! Had to use quite a few of THOSE words tho'. Finally located the screws retaining the coolant tank above and behind the tire in the inner fender beneath a 27 year buildup of caked-on gunk and and road dirt. Tank finally came on out.

The tube nut holding the accumulator to the evaporator presented the next big problem. I couldn't get a straight shot at it from above and the straight open end 1-1/16" combo wrench kept slipping off the nut. I finally took the offset box end of the wrench to a grinder and wore a 3/4" slot in it to turn it into a tube fitting wrench. Nut finally came loose, 1/12 turn at a time.

The hex head sheet metal screw holding the accumulator to the fenderwell was installed by a 2" tall Vietnamese robot at the factory in a place unaccessable to normal sized human hands on a 6'-2, 215 lb. shade-tree mechanic, finally worked a 5/16" micro ratchet combo wrench on it and rotated the 1-1/4" long screw out 5 degrees at a time while dripping blood on it for lubrication.

You were right Ken.... It came out without pulling the evap box..... except it came out from the top of the RIGHT fender!!!

I got it all back together after 7 hours of beer, blood sweat, profanity, and tears. Then found that the lo side service access port was too close to the tensioning clamp nut on the compressor mount and the R-134 quick-connect and adapter crash with the nut making it impossible to get the R-134 charging hose on. NOw I gotta find a R-12 hose assembly with a right angle fitting on it to get on the service port and mutate that onto a R-134 hose, pull the system down with a vacuum pump and gas her up and pray for no leaks.....after I figger out why there is no 12 volt signal going to the pressure switch when I call for A/C in the cockpit......

One more....... there are 2 wires going to the compressor, one light green, one dark green and 2 push-on spade terminals on the compressor with a 3.8 ohm reading between the two of them, neither common to ground. Anyone know what the extra wire is for?????

Still ain't done, but farther along than I was a week ago. I ache all over!!!

Happy Easter!! (NOT!!!!)

Dave

Oh yeah...... when I ran the oily flushing goop thru the system then blew it out, including the residaul oil with shop air, it sprayed all over and soaked my wrapped header tubes. Smoked and smelled like it was on fire all the way home.................

Damn this is fun!!!!

I have no idea why I said left.  I know better of course.  I really get on my students for that.  Shame on me.

But other than the stupid slip,  I glad you got it out.  Now to get it back together.  Gotta love that burning stench.

I drove it in today and I guess I burned all the stink off the pipes. Any idea what the second spade connector on the compressor is for??

I'm just gonna run 12 volts from the battery to both terminals, one at a time, and see if it runs. Hope I don't smoke it!!

Dave

Ken,

PS: Still can't find a right angle R-12 hose.....

Got the air charged up last week,seems to work ok, had 38 degrees at the center vent. I'll try it on a warm day and let you know how it is.

I just road tested it today after a total rebuild, the more I ran it, the better she ran. Poor the girl sat here for 5 years.

Denny     

Found a R-12 hose with the angle connection and got the R134 A/C up and running last week, only problem now is it only blows through the floor vents. I guess I have some vacuum tracing to do. Pain-in-the-butt job, but someone had to do it!

Dave

Hmm. Where did you find the right angle hose? Sure would make the conversion easier.  I had to weld one up and it isn't "pretty".

Glad to hear you got it all worked out.

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C3: 1979 Corvette Coupe, Auto, L-48, Red/Doeskin (my wife's fave);

I found it buried in my pile-of-good-stuff-I-don't-need-anymore-but-can't-throw-away . Everyone has one of those! Seriously, I think I bought it at AutoZone 10 years ago to recharge my 944. Refrigeration supplu houses should have them. It's a 45 deg. fitting, but gets on the port.

Dave

Thanks! I'll see if I can track one down.  Probably wait till I need to work on it again to install it. Like yours, mine only blows cold air on my feet so I am going to have to dive into the dash to see what vacuum/mechanical problems I have to correct.

Shane

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C3: 1979 Corvette Coupe, Auto, L-48, Red/Doeskin (my wife's fave);

I finally broke down and ordered the complete set of factory shop manuals from Helms. 4 books, over 3,000 pages so I guess they must be pretty detailed. likely the best hundred bucks I'll ever invest. I'm not doing anything till the manuals get in. The Hayes manual just doesn't cut it!!

Dave

 This whole thread has me a bit confused.

 My system is already vented. Hose to the compressor was removed. So there should be no R12 left in it.  My questions:

 Do I or do I not need to change the compressor?

 Do I or do I not need to drain the oil?

 Do I or do I not need to change any other components?

 Sorry if I'm opening up Pandora's box but I see lot's of differing points of view here and since I'm not an AC/HVAC guy....

 Hope ya'll can sense and understand my frustration here. Is there one answer to all these questions ? I see many in this thread.

  Jim

JimG38452.4922453704

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Lifetime Member #73

The Money Pit.... and my niece

(click to see a slightly larger version)

Jim

The conversion from R-12 to R 134 does require some new components. A new dryer, compressor & O rings is the least you can get away with... the system should be flushed with an air conditioner cleaner. If you don't know much about air conditioning you could flush the system install the new dryer ( don't hook it up as it will take in moisture from the air & be ruined) install new O rings & the compressor. Then take it to an air conditioner shop and they could check you system for leaks & load it up. The cost that way probably wouldn't cost that much.

Alan

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Jim,

You may or may not need a new compressor. The R-4 pancake job is under $150.00 rebuilt at Advance or AutoZone, so it would not be a real bad lick if you did replace it for insurance....... or you could try the old one and hope! I wasn't sure if my old compressor worked or not and bit the bullet and swapped in the rebuilt unit. It had been open for a long time and had no belt on it when I got the car.

You do need to drain the oil from the compressor and accumulator, blow out the system with shop air then flush the system with the special snake-oil, let it sit for an hour or so then blow it out with shop air. Snake oil flush is about $15.00 for a spray can full enough to do the job. (DON'T include the new $45 accumulator in the flushing!!!)

All the required seals come with the new accumulator and compressor. The accumulator is a real pain-in-the-butt to get to but doable!!! Your '79 is probably identical to my '78.

I got mine fired up and it worked like a champ......... for one day, then leaked down to zero over a weekend, so I have a pretty big leak somewhere. I got a leak test kit with freon mixed with some phosphoresent goop that glows under black light, but have not dug into it yet.

Dave

PS:

It takes about 8 oz. of oil, installed per the instructiuons with the new compresssor.

Everybody has a different way to switch over to R134, I think Alan is on the right track, the compressor may not have a seal in it to work with 134. You might see if you can change to over.

I'd go one more step, replace the hoses, most new ones have the vapor barrier in them to handle the R134.

I started this thread, seems to have lot's of input, keep it up guys, maybe we will all be cool this summer!

Denny