Review of my plans for the AC system, comments welcome
 

I want to post and recieve comments about the rebuild of my AC system.

I have done the typical search but would like comments

I have done just about everything thing to a car but work on the AC system. I was going to get my 609 license but while studing for it I realized that R134 was probably the way I wanted to go (see below). I may still get the license for the SL.

I am working on the 1982 300TD. The conversion to R134 was done about 2 years ago and done incorrectly, I know I did it. I added R134 oil and freon with out flushing or removing of oil. So I now face a contaminated system that will have to be rebuilt. The conversion to R134 was done due to a evaporator leak. It was found by the Dealer with a sniffer. I decided to do the 134 conversion to save money, I thought. The car was an airport car and driven about 2000 miles a year. Now it will become a daily driver and the AC must work well.

This is what I plan.
1. A new R4 compressor.
2. New dryer
3. New evaporator
4. New expansion valve.
5. New parallel flow condensor since I will be converting to R134.
6. All the hoses rebuilt at a local hydraulic shop.
7. New high/ low pressure switch.
8. New O rings with Nylog ( R134).
9. New oil and of course R134a
10. The hydraulic shop will build 2 hoses to allow the new condenser to "fit " to the Mercedes hoses. I want to take this approach so that any future condensor replacement will be a easy job. The alternate is to custom make the main hoses or add a manifold to the condensor so the connections are in the current position. The condensor will be from ACKITS.COM

As I said I want the system to work well since this will be my Wifes and my daily driver.

ANY advise on the removal of the evaporator would be appreciated, I understand its a bear.

R134a vs. R12. I know the sytem is designed for R12. The thought process for converting is so that the car can be a DIY. I understand that the problem with the R12-R134 conversion is a lack of condensor size. Stu Ritter of MBCA fame recommends wiring the AC condensor fan to the compressor clutch. They then find the R134 conversion to be acceptable. I want to solve this problem by going with a larger capacity condensor. So the system will be able to handle the R134. Size for size the parallel flow condensor is 33% more capable then a serpentine unit

The sytem will be dismantled.
All hoses flushed, then rebuilt, then flushed again.
Evaporator replaced, and anything in the dash area that needs replacing will be replaced.
New expansion valve.
New compressor installed with the right amount of oil and once the system is closed rotated to prevent hydraulic lock.
I understand about the oil being hydroscopic and will keep its exposure to the atmoshere to a minimum.
All O rings will have nylog (R134) applied.
The system willl be evacuated to 28" here for Dallas, 603'MSL
Then the R134a will be added by weight.

The last 2 items I may not do depending on the cost of a scale and the vacuum pump. I know the compressor type unit is cheap at Harbor Freight and I have a 6HP compressor that can run the cheapo vacuum pump. I will have to look at the scale cost for this one job.

I may consider an inline filter just for insurance. But with everything new I doubt it will be necessary, as long as I adequately flush the hoses.

My decision to go with R134 Vs. R12 was partially due to the cost of the OEM condensor. Even at Rustys or Fastlane it was $250. The aftermarket unit is $85 at ACKITS.com. The hose assembly to make the aftermarket condenser attach to the Mercedes hoses will be about $60 from the hydraulic shop, they say. The aftermarket Parallel flow condensor has the fittings at the top and bottom of the condensor. The Mercedes unit has it in the middle so some kind of adaptor must be made. The hydraulic shop said that they could weld tubes on the new condensor to place the fittings to the correct place. I did read about having to replace parellel flow condensors with compressor failure due to the small orifice size that is use in the parallel condensor. I would rather make up a hose manifold for the connections which would allow easy condensor R+R.
The current condensor is not leaking but sort of beat up, dirty, bent fins and original. It has also had the R134 oil and the R12 oil in there so the acids may have been eating away at the unit.

I have ordered the "new" CD from Mercedes ( its only $99 for the 123 CD) that will have the AC manual and the Electrical manual that I don't have. When It arrives I will surely have more questions.

Any and all comments and suggestions will be appreciated, Maybe not liked, but appreciated.

Dave

Dave,

I offer my comments with all due respect. Please don't take offense if I sound sarcastic or anything.

To begin with Stu Ritter does not live in the DFW area where we have an annual heat wave that lasts four months.

You can use a parallel flow condensor and still use R12, it will be all the better.

You are looking at putting some major bucks into this project for obvious and justifiable reasons. Given the overall cost of R12 would represent less than 10% of the overall project cost.

In fact to help you save some money and basically "pay" for the R12 I will loan you my vacuum pump. I am moving toward recovery/recycle machines for my vac pump function and can let my vac pump out of the shop for a week or two when you get to that stage of the project. If you would be charging from a bulk can I would also loan you a "dial a charge" which some folks prefer in place of a scale.

I have converted several 123's with reasonable results, but those results were marginally acceptable because my family and I live 20 miles out of town and do stoplight to stoplight driving VERY rarely. In the DFW area in town driving is almost impossible to avoid.

That said, I have reverse converted one of them.

Other problems with 134 conversion is getting the oil right, and the pressures for that matter. The chance of long term system survival statistically goes down in a converted system. The sightglass becomes close to useless in a converted system, and it usually takes experimentation to get the charge right, even if you carefully meter in what you think is the right amount of 134, you will most likely have to experiment a little by monitoring high side pressure. Once you achieve the right charge, there is no good way to duplicate that volume next time because you don't know exactly what it is. That means experimenting again if you have to charge again later.

An additional comment is to buy a NEW R4. I've been there, done that with rebuilt R4's. If you insist on a rebuilt, do some research and buy one from ackits or somewhere, definitely not a chain store unit.

Best of luck with your project regardless of refrigerant choice and let me know if you want to borrow my pump and dial a charge.

Have a great day,

AHHH! the plot thickens.

I will use a NEW R4 Ive heard the stories about rebuilts failing in 1-2 years. That is not the intent of the rebuild. I want to do it once and do it right. So I don't have to worry about it.

I may use the parallel flow condensor and the R12.

I'll start to think in that direction.

Got to go fly a trip and think about my R12 license!!!!!

Dave

Dave -

I think you've got a good plan. Feedback from those who have used a parallel condenser is that R-134 provides reasonable performance. Certainly R-12 is ultimately better, but it may not be truly necessary. At any rate, getting the 609 license is trivially easy - I've had mine since before the internet...

I think the limiting factor in around town performance is the compressor, rather than the refrigerant. At idle, the low side pressure rises to ~45PSI, which means evaporator temp is about 45 degrees. Typically discharge air is 10 degrees above evaporator temp, so think 55 degree air. This is about the upper limit before the air begins feeling clammy rather than cool. I don't know of any way to solve this problem, other than move to the sticks like Larry :)

One advantage of staying with R-12 is that you don't have to use PAG oil. PAG is nasty stuff - it's a skin and eye irritant, and of course it is very hygroscopic and will certainly introduce water into your system.

One suggestion. The 123 chassis was designed by MB to utilize 80% recirculated air/20% fresh air when in recirculate mode (basically all summer here in Texas). It can be modified to use 100% recirc. I did this back when I owned a 123. I found this mod reduced duct temperatures about 5 degrees on the hottest days. It's quite easy, and well worthwhile. I may have the instructions buried somewhere on my PC.

I've got a vacuum pump and guages, which you're welcome to borrow as well. I bet Larry's are better :) That said, our offices are across the street from one another (I'm looking at Larry's building as I type this), so it's not like you can save a bunch of driving.

Gotta run to a meeting.

- JimY

I have a couple comments (I am the guy who converted his '84 300D to a parallel flow condensor and 134a):

1) Is there a particular reason you are going to replace the evaporator? You said it was just replaced a couple years ago. If it isn't leaking then all you need to do is flush it and you'll be fine. Replacing a perfectly good evaporator seems like a waste of time and money.

2) Definitely have the a/c shop install a filter.

3) I did the 100% recirc trick and didn't like it. Here's why. People say there is 80/20 recirc., and I found that not to be true. What happens on my car is the recirculation door opens and closes on some cylce (the system does it automatically). Sometimes the door is closed completely, giving you 100% recycled air, and sometimes it opens, giving you a mixture. I closed it completely for testing and DID NOT notice a significant change in a/c temperatures - maybe only a degree or so. Besides that, I really was unsatisfied with the fact that I had somehow butchered my car and undid something Mercedes had desinged it to do. If you repair the a/c system properly, you WILL have good cooling without jury-rigging the recirculation door. Lastly, its nice to have outside in the car, which you won't have if you alter the system.

4) Jury-rigging the electric fan may be a good idea, but try it first without doing so. If everything is working properly, it will turn on when it is needed, but you can test it later and see if your vent temps are lower. I prefer leaving the car stock when possible.

4) Like everyone says, just go with the r-12. The on-line test is not difficult, and if you are serious about doing the best job you can, you won't waste your time with 134a.

GregS
'84 300D, 174k
'90 300CE, 164k

It's been a while, but as I recall the 100% recirc modification on the 123 involves the fresh air door, not the recirc door. As designed, the fresh air door is open whenever the climate control is switched on. The recirc door selects either 100% fresh air or 80/20, depending on which position it is in. The modification involves closing the fresh air door whenever the recirc door is in the recirculate position.

I wouldn't worry too much about fresh air in the 20 year old car. A car that age has plenty of air leaks from tired, old, shrunken gaskets and seals.

I measured the performance differnce the change made, so I can state objectively the effect it had. (I keep notes on this stuff.) On a hot Dallas day (105F) it reduced the duct temperature from 58F to 53F. That is enough of a change to be easily noticable; it makes a significant increase in comfort.

Perhaps you don't live in a hot enough climate to require such a change, or perhaps you misunderstood how to perform the modification.

- JimY

I've "reversed" refrigerant in two of em in the past few weeks. 1982 240D and 1985 300D (got rid of DuraCool in the 300D) and if the ambient conditions are under 90 they will both freeze you out:). I am scheduled to do a 1986 Chevy pick up this weekend.
Do what you gotta do and stick with the R12.

Whoa there big fellas!!!!

I knew I would get a lot of info. Let me let you know what I have considered.

Larry
Thanks for the info and ability to borrow the vacuum pump and the "dial a charge". I think I'm going to go with the R-12. (good boy they all say, What a man, A true R12 man *G*)
I wil get the 609 license and then be ready for the 300TD and the 560SL.
But I am still thinking about the parallel flow (PF) condensor for better cooling and to save $200.
My understanding of the AC system is that the R134 freon can not be cooled suficiently in the serpintine condensor due to the design heat exchanging ability of the unit. It was not built to exchange the calories that the R134 needs. By using R12 in the PF condensor I will ensure that the R12 is completely sublimated from gas to liquid, even though it may be 110F outside. The stop and go traffic in the metroplex agrivates this by reducing the airflow over the condensor. By using the PF condensor I will help the system provide adequate liquid freon to the expansion valve therefore allowing the evaporator to have the necessary cooled freon liquid to expand. By using a larger capacity (a PF condensor) I will make the system work better.
Do you see any system problems using the PF condensor with the current 123 setup which I will be renewing?

Jcyuhn
I will look into the ability to close the fresh air vent completely. Can this be done after the dash is reinstalled or does it have to be done while I have the interiors of the car out?

GregS
The evaporator was NOT replace by the dealer. They found a leak that was small. I had them remove the R12 and I put the R134 and 134 oil in the system. Then every couple of months I was going to top off the system. So the evaporator is still leaking and will need to be replaced.
Would you still recommend a filter when everthing in the system wiill be brand new except the metal sections of the hoses, which will be flushed completely?

moraine
I will check with Tim at ackits.com. but now I have been "saved" and will go with R12.
I would still like to go with the PF condensor. Unless you guys can convince me to spend $200 more for the OEM replacement.

To all

1. A NEW compressor
2. R12 R12 R12. R134 is the devils work. Say amen. *G*
3. I will rebuilt the hoses, they are 23 years old.
4. Condensor is also 23 years old and will be replaced, the acids have been sitting in them
5. Flush Flush Flush and Flush again. Ok another amen.
6. I will look into the fresh air door modification. again If anyone has the specifics please let me know.

Well I hope I have not offended anyone.

I just bought R134 guages form Harbor Freight, I'll have to return them. I will work on the 609 license and start taking this system apart. order the necessary items ( talk to ackits and Rusty) and get moving on the project. any other words of wisdom will be great.

Now who was going to help me with the removal of the dash and center consol?????

Once I get the service CD I'll have questions I'm sure.

Dave


Ahh questions all ready

1. Tightening the fittings. Double wrenches, but to what torque? Do you actually torque them with a torque wrench or guestamate them?

2. Methods of keeping the moisture out of the system? I'm sure you use caps on all the components. Hoses, dryer (should come with caps?) compressor? evaporator etc. What methods do you seal the various parts with.

3. Applying nylog, How much and where? Orings? threads of connectors? etc.

4. Does the Service CD have an exploded view of the evaporator section. If so could someone Email it to me dwmorrison@attbi.com

thanks guys

Dave -

One more thought. Not to pile yet more work upon you, but consider replacing/rebuilding the vacuum elements while you have the dash apart. At the bare minimum replace the element for the center vents - it's inaccessable without removing the dash, and is usually the first to go. My hazy recollection is the other elements on a 123 can all be replaced without pulling the dash. (Someone please correct if I'm wrong.)

Modifying the system to use 100% recirculated air is quite simple, and does not require dashboard removal or any surgery. It's about 10 minutes work and requires about a dollar worth of parts. It is completely reversable should you not like the results. Here's a link to an article I wrote (in 1999!) on how to implement it. This is the archives of the original mercedes mailing list, which predates this bulletin board by about 7 years...

http://db.mercedes.cx/mb/199904/15/0010.html

The searchable archives of the mercedes mailing list are available via http://www.mercedesmailinglist.com

Good luck and enjoy,

- JimY

ps - I vote for the parallel condenser too. Why spend extra for the MB unit?

jcyuhn
I do believe in doing it right the first time. My Father taught me this because he was so cheap that he once tried to epoxy a fuel pump diaphram to see if it would work. This drove me nuts and I learned to do it right the first time.
I will look at everything as I remove the dash and take care of it as I go. The elements will be replace because I'm there. I sort of did this with the suspension rebuild. EVERYTHING in the suspension was replaced. It lasted 23 years so the next 23 years I don't have to worry about my suspension.
My sons 65 Mustang turned into a 2.5 year restoration due to the inevitable "while I'm at it itis" that comes with car repair.
The 300TD is turning into the daily driver. Were going from the 99 E300 as a daily driver to the 82 300TD ( I'm a pilot for American Airlines, Were still not out of the woods when it come to filling for chapter 11. Its looking better, but were not celebrating yet. so the 300TD will be the car of choice for the next couple of months/years) So the 300TD needs to be in great shape. Its hard to go form 99 E300 luxury to the 82 300TD and " not notice". A suspension rebuild and a cold AC in Texas will make the transition easier. I've owned this car since 1990 and have always liked it. So this just presents the opportunity to "restore" it to the level I want it.

I have saved the sites that you have shown and will look at them tomorrow.

KEEP THE INFO COMMING GUYS

Thanks

Dave

And here's similar info as presented above, only for the 126 car. At this same site there's also discussion on parallel flow condensors:

http://business.baylor.edu/Richard_Easley//autofaqs/recirc.htm

Dave If it is any encouragment, a 300TD that is right (suspension etc all refreshed) is a great driver. Mercedes sold a ton of them and theres got to be a good reason.

I recently rode in a 1978 240D with 78k miles. I was very curious what it was going to be like. The 123 model cars are remarkable. I quickly enjoyed riding in the 78 and remembered why I bought several of them.

Keep us posted,

Haasman

Dave,

The nylog only needs to go on rubber parts, you need not use it on threads and such.

You don't need to torque the connections, just snug them up tight with a back up wrench.

The parallel flow condensor for LESS money is a no brainer. Since you have to replace the condensor anyway, and your building new hoses anyway, you will not only save money but also will have a more efficient system. Although there are other variables, the "capacity" of any air conditioning system is almost always determined by the condensor heat exchanging capability.

I have to pass on your offer to let me share in the fun of tearing apart the dash. I think that would just be more fun than I could stand.

Good luck,

Dave, it looks like you're seeing the light. One thing I want to mention that has not been hashed over is the vacuum pump. I'd suggest you borrow Larry's pump rather than buy the compressor operated one. We had a debate about this recently and he won. I have the Robinaire pump, which is supposedly better then the Harbor Freight unit. When the subject was debated, I went out to the garage and tested the pump. It managed 27" with nothing connected but the gauge set and I'm virtually at sea level in Florida. The compressor ran continuously, so leaving it on all day would not be a nice thing to do to it.

If you need to hear it again, the parallel flow condenser with R12 sounds like a great thing.

The R12 license online is ridiculously easy - had mine in under 1/2 hour.

A couple more comments:

-I have the PF in my car and I can't think of any drawback besides the nuisance of fabricating custom hoses. Go for it.

-If eveything is going to be new, what is there left to flush? You already have a huge job ahead of you, so don't make it worse than it already will be. Still go for the filter though.

-I stand by my comments on the recirc. door "trick." No disrespect jchyun, and maybe my car is special, but it didn't work. I used your link a year ago to do this mod., and on my car the system would cycle a couple times and then the recirc. door would no longer open and close until I turned the car off. Something in the switch system would not allow my car's doors to open and close as you claimed they would. I drove around for a couple days with the glovebox out just so I could easily observe what was going on and to be sure of my conclusion. If it were my car, I would maybe rig up the electric fan to turn on when the compressor is running, but I wouldn't bother with this particular mod.

-When I did this job the advice given by the guys that sponsor ackits.com was to use Nylog on, and I quote, "everything." O-rings, threads, service valves, service valve caps, etc. It can't hurt.

-Just snug up the fittings with the wrenches. These are all light aluminum fittings, and the o-ring is actually doing the sealing work, so don't go too hard on the fittings.

GregS
'84 300D, 174k
'90 300CE, 164k

ackits.com has some great people behind it, so no disrespect is meant toward them, but Nylog is an o-ring sealant, not a thread lubricant.

Have a great day,

Definately go for a real vacuum pump; whether borrowed, rented, or purchased. At sea level, 27" of vacuum only brings the boiling point of water down to about 115F. (I'm interpolating from a chart here, so give or take 5.) It'll get enough air out of the system that it will cool OK, but it won't boil all the water out unless your garage is a lot hotter than mine.

In contrast, I own the bottom of the line Mastercool vacuum pump. It's a 1.2 (I think) CFM single stage rotary vane pump. It's rated to pull 200 microns (which isn't even close to the dual stage pumps, which are good for 50 microns.) At 200 microns, water boils at -24F. You could dehydrate the a/c system in the middle of a midwestern winter with one of these things. I snagged it for $199 at a McParts store - couldn't pass up a deal like that.

I'll try to attach the .gif...

Regarding the recirc modification. Sorry it didn't work for you GregS. I can't figure what could be the problem - the change powers both doors off a single vacuum port, so one should be open when the other is closed, and vice-versa. Worked nicely on my 123. Did you test the two actuators to see if one had a vacuum leak? Of course, here in Texas my car just stayed in recirc mode from June until September. At least it's easy to install, and easy to undo.

Cheers,

- JimY

Larry,

Don't forget that some of us up north have very harsh winters with lots of salt on the roads. We need something to prevent fittings like those on a/c components from rusting themselves solid, and Nylog does a beautiful job of this. You can use anti-seize, but I find it very messy.

There are rubber seals on valve stems and valve caps, which is why its also a good idea to use it on them. I just had to replace a valve stem on my r12 300CE which may not have leaked if it had Nylog on it (the new one does!).

GregS
'84 300D
'90 300CE

Ok lets continue with more questions. Primarily on technique.

1. When replaceing a single part on the AC system you install oil into that part. It is an assumption that the amount of oil in that one component, lets say the condenser, should contain a fraction of the total amount of oil IF the system has the oil in suspension when the system was shut off. Since I'm R+R everthing. I will place the total recomended amount of oil into what component? I will find the total amount in the Service manual. Is this correct?

2. The Condenser. I have found that Carlisle in San Antonio has a 16 X 22.5 parallel flow condenser. Which should be better that the 14 X 22.5 that ACKITS.COM has. They said the unit is a 6mm size unit. I want to make sure it is not a tube and fin or a serpentine unit. Are parellel flow condensers labeled as 6mm units or what? The size would be great but I don't want to get an inferior condenser.

3. Flushing the remaining parts. I will have to flush the metal sections of the hoses. What to use. I have read about using Paint thinner, or laquer. Or should I buy "flush" from ACKITS.COM. Or should I use the paint thinner and a final rinse with a flush?

4. Is there a better evaporator to buy? should I get after market or should I buy the unit from Mercedes. Does anyone make a unit that will last longer, like 23 years isn't long enough.

5. I will install an inline filter. Cheap insurance.

6. Drier. any manufacture better than another?

7. Hoses. Should I specify a certain manufacture of hose or kind? To my knowledge the barrier type is not required for R12 nor R134a retrofit, only R22 and its debated about the NEW hoses in R134a. Is this correct?

8. Compressor. I will be buying a NEW R4 compressor. It should come with oil in it. If not I know it will specify that. Should I still flush the compressor? To make sure the oil is fresh? I know to hand rotate the compressor to prevent hydraulic lock. Since it will be R12 I will be using mineral oil. Any particular manufacture for the oil?

9. Method of assembly. The evaporator will be installed along with expansion block and capped. The hoses will be led through the firewall and can then be attached ( with new R12 O-rings and Nylog ) to the evaporator and the expansion block. The other end of the hoses will be capped. Each component will be installed with caps and the hoses will then be uncapped, nylog applied to the O-rings and the connection tightened. Any particular methology in the assembly or just keep the components capped as you assemble the system. Uncap the individual unit as you get to it for connecting.

10. Vacuum the system for 1 hr minimum. Over night is best. Look for a vacuum of 29.92 inches. Adjusted for the 603' msl elevation here at DFW. This vacuum should hold for 30 mins after wards. They say to break the hose seal on the vacuum line to prevent the oil in the vacuum pump from being sucked into the sytem. Don't you close the valve on the center line to accomplish this? then you can unscrew the vacuum pump from the guage assembly. Is there a purge valve on the vacuum pump that will allow air into the pump after you close the center line valve?

11. Apply the R12. some article say to add it by weight some by using guages. Larry offered to allow me to use his "dial a charge". I have not used one of these before. Any instructions would be great or a link to an example would be great also. guage pressure shoul be in the Mercedes Service manual based upon outside air Temp. Correct?

12. (edited for two additional guestions.) I bought R134 guages that come with adaptors. http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=39248
I got these for $50. To my understanding there is no difference between R12 and R134 guages except the quick release fittings on the R134 units and maybe some OAT references on the guage. These guages seem to be R12 except for the blue hose color. The fitting seems to be R12 size. So these would work?????? If not does anyone want to buy them. $50 plus shipping. or I'll have to return them.

13. I have the quick disconnect fitting in the low side hose as per the R134 conversion. How do I remove this fitting?

Thanks Guys

Dave

Dave, I can answer some of the questions:

1. Since you are completely flushing everything, you don't need to put various oil quantities in individual components. After putting everything together, disconnect the low side line above the compressor near the front of the injection pump. Then pour the required quantity of mineral oil in there and immediately connect the fitting. Then as you say later, turn the compressor ten or twelve times by hand to distribute the oil. Replacing quantities in individual components is for when you are replacing ONLY that component.

2. I can't help on this one. I'm sure that ackits or Carlisle can give you good advice here.

3. Probably the most convenient to use is Brake Cleaner because it comes in a spray can and you can just use the spray can to blow it through. If you use mineral spirits or such, follow it up with regular a/c flush to get out the oily residue. THE IMPORTANT THING HERE IS TO GET ALL OF THE FLUSHING AGENT BLOWN OUT OF THE SYSTEM.

4. Can't help on this one. I like your thinking. The original lasted 23 years. To my knowledge the 123 evaps were okay, it was the ones in the 124's that were bimetallic and gave problems.

5. Make sure you use it on the suction side and that it has adequate flow.

6. I think one is as good as another.

7. Barrier is not required. McCains could probably just replace the hose on your original fittings or make the new ones for your parallel flow.

8. I can't remember if it will have oil in it. If it does, you will have to be ABSOLUTELY CERTAIN that it is mineral oil. The only way you can know FOR SURE is to pour it out, rinse with mineral oil, pour that out and then put in the specified amount of mineral oil.

9. Your method of assembly is very good.

10. I think that if you evacuate this time of year, components are hot enough that a good vacuum will boil off the moisture of a clean system with fresh oil in 45 minutes or so. The real need for overnight evacuation only comes with a dirty system in cold weather.

11. To use the dial a charge, you evacuate it just like a system, then put in the required amount of refrigerant. Once filled you then charge the system from the top valve. If the system starts slowing down in its drawing the charge, you plug in the dial a charge heater to boil the rest of the refrigerant out of the vessel.

If you are charging from cans, you can use the number of cans to determine the volume. If you are charging from bulk, the dial a charge is handy. That said, however, since your system is staying R12 and you have a sight glass, you can get it right by simply charging and watching pressures and sight glass. Once the sight glass is clear, you are there.

12. There is a good bit of difference between the gauges. First the temp scales on 134 gauges are for 134. Second, the manifold fittings are 1/2" ACME. R12 gauges and hoses are less expensive than 134. If you think you will ever be doing a 134 system, I would recommend hanging onto them and getting an R12/22/502 set and keep them both. You don't want 12 in your 134 gauges or vice versa. Keep them totally separate. The refrigerants are completely incompatible, so you would be cross contaminating if you ever used the same set on both refrigerants.

13. I am not sure if you mean the a/c system on the car or on your gauges. On the car, you will need to remove the adapter and put a shrader valve in the 1/4" inverted flare fitting. I don't know if you are talking about the gauges. As I said I recommend having sperate gauge sets. A few years ago it was even recommneded to have a different set of 134 gauges for 134 with PAG oil and another set for 134 with Ester oil. This practice seems to be either ignored, or it has been found to be unnecessary. I hope the latter is true because I've been using my gauges for both PAG and ESTER.

Good luck and enjoy,

You've already have a great plan and gotten great advice.

Three things:

1. Are you absolutely sure that the evaporator is leaking? They really aren't problem parts on 123s - I seem to recall stevebfl saying he never had done one where the evaporator was the issue. No sense in spending the money if you don't have to...

2. The online 609 certification is as easy as everyone says, and well worth it.

3. It goes against convention, but I charge refrigerant by measuring the output temperature from the center vent with a $10 digital thermometer I got from Radio Shack. I just keep adding R-12 until the vent temperature plateaus. I figure that since the goal is not to have a particular amount of refrigerant in the system, but rather have the coolest temperatures from the vent, this is a more direct way of measuring. I've always gotten good results this way.

Good Luck.

This is a great thread.

I stumbled onto a product that may be of value here. There are a few articles with pics on how to repair or fabricate A/C components.

Good Luck.

http://www.muggyweld.com/super5.html

#1) You might want to check into this. I was told (again, by ackits.com) to install the required amount into the compressor, 2oz in the r/d, and the rest evenly throughout the system (which I think equated to some in the condensor and some in the suction hose). It seemed logical to me to evenly distribute oil throughout the system.

#2) I went with the 14x22 inch condesnor because it was the closest size to the original. It fits nicely, but as you know, the bigger the better. I think it would be really tough to fit a 16" unit in there. I would say you definitely would need those fabricated hard lines to bring the top and bottom condensor fittings down to the opening in the frame. With the 14" unit, I JUST barely had enough room to instal custom made rubber hoses (one runs directly from the bottom fitting on the condesnor to the r/d, and the suction line connects to a separate "S" shaped hose that connects to the top fitting on the condesor). And even then I had to open up the bottom of the opening in the frame to make it work.

Good luck,

GregS
'84 300D, 174k
'90 300CE, 164k

If you have the system all apart anyway, maybe you could put the last connections on after pouring the share of oil in the component. The problem is that you will be exposing the hygroscopic oil to the atmosphere for a longer amount of time. The R4 123 cars have a very convenient place to pour in the oil and immediately close the system. That is at the low side connection above the compressor and near the IP.

I have poured all the oil in the compressor before and then distributed it by turning the compressor by hand 10 or 12 times. One time after doing this, I immediately after running the system for a minute or so, had to dismantle the system (don't ask.) The oil seemed to be all through the system as if it had been running for years. Maybe this was a fluke, but it seemed to me that the oil distributed quickly and the compressor was certainly not starved for oil on start up.

Have a great day,

I've learned so much from the AC "experts" on this forum. I being a beginner in AC repair have only one thing to add to all that the experts here had to say:

Change the fuse (in the fuse box) for the condensor fan. Fuses actually do wear out eventually and then fail even if they were not subjected to excessive current. In a R134 converted system this is particularly important cause the pressure could go way too high if the fan does not kick in when it is supposed to. Small insurance to replace this fuse even on a R12 system.

Speaking of fuses make sure you have a spare glow plug fuse strip (80A ?) in your spare fuse kit. (I keep a spare set of assorted fuses in the glove box). The fuse strip is cheap but they are not available at your Pep Boys, etc car parts store so best to buy in advance.

The old link is dead here is where you can find the 126 recirc info.
http://web.archive.org/web/20020811120350/http://business.baylor.edu/Richard_Easley/autofaqs/recirc.htm

Link fixed.