Review of my plans for the AC system, comments welcome - Page 2 - PeachParts Mercedes-Benz Forum

#16 06-06-2003, 07:09 AM

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,

jcyuhn · #17 06-06-2003, 11:00 AM

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

GregS · #18 06-06-2003, 03:27 PM

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

dmorrison · #19 06-09-2003, 10:20 PM

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

#20 06-10-2003, 07:40 AM

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,

tjohn · #21 06-10-2003, 08:28 AM

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.

RickM · #22 06-10-2003, 10:50 AM

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

GregS · #23 06-10-2003, 04:55 PM

#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

#24 06-11-2003, 08:15 AM

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,

erubin · #25 06-13-2003, 07:14 PM

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.