The standard opinion of professionals and the instructions on the part...and the instructions in the MB FSM all agree that if the system is opened up you need to replace the rec/dryer.... It has a certain amount of silica jell ( there are two types I think... but for demonstration purposes only...as they said in the Army ) and it is in oil.... it has a high capacity for attracting moisture... which is what it was made for....and no way to get it out... due to it being in oil... dry silica jell can be reversed...and is in fact used that way to dry flowers... you can heat it in the oven to get the moisture out...then dry stuff with it again...
If you have a great pump an hour might be fine... but what is the rush... the consequences of leaving moisture in the system is severe... the cost of the REc/dryer or a couple more hours of watching the vacuum pump... negligible.

I'm definitely NOT arguing with this. BUT, the amount of time you have to pull the vacuum depends on the pump you are using. For example, if you have a 6 cfm 2 stage pump, it will probably dry out the system in less than half the time of a 1.5 cfm single stage pump. I spoke with a technicion at Arizona Mobile Air (www.ackits.com) who said they use 5 cfm dual stage pumps and generally pull a vacuum for only 30 minutes.

By all means if you aren't sure, the longer you pull the vacuum the better. I'm just throwing that out for educational purposes.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

One more thing, in addition to the type of pump you are using, your system's set up also determines how long to pull a vacuum. For example, on my 911 it has front and rear condensors. I pulled a vacuum with my 1.5 cfm pump for 3 hours yesterday to thoroughly dry everything out.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

OK, I have a side question... If you just have a vacuum pump and not a complete AC machine, how do you remove all the freon from a system, store it so none is released and then re-introduce it into the system when you're done? If you aren't supposed to re-use it, what do you do with the old stuff since you can't release it into the wild?

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

Are you changing the type of refrigerant in the process? I mean was the system charged with R12 and are you planning on retrofitting to R134 or some alternative refrigerant? If so you should really flush the system while it's open and replace the receiver/drier and think out about doing the expansion valve as well. Then refill with the correct oil, seal it back up, vacuum and recharge.

If you're not changing refrigerants and just need to pull a vacuum and charge it up I have a vacuum pump and a set of gauges and also live in Lutz. If you feel like stopping by the house I'd be happy to evacuate the system for you. Shoot me a PM if you're interested.

-Frank

I would take my vehicle into an indy who still does r12 (if thats whats in there) and have him evacuate the system, then do the rest myself. I'm not sure, but I think they have to do it for free?? Because the EPA doesn't want this stuff vented. Besides the shop could recycle the R12...

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For Sale: 1982 MB 300TD
1995 Chevrolet Suburban 6.5TD

Sold: 1980 IH Scout Traveler- Nissan SD33T Diesel

Unless you have a way to condense the R12 that you are evacuating from the system you can't.

After a couple of A/C problems over a two year span I ended up buying a used Sun R12 recycler (MRC-300) on e-bay a couple of years ago for the princely sum of $100. It has an internal vacuum pump for evacuation and its very to use and has worked flawlessly for me but it has two major drawbacks.

1) It's kind of bulky to store - its not the kind of thing you want if you have limited garage space.

2) Ever since I bought the machine I've had no A/C problems at all... but I have used it on friends cars a couple of times.

__________________
98 Dodge-Cummins pickup (123k)
13 GLK250 (135k)
06 E320CDI (323K)
16 C300 (62K)
82 300GD Gelaendewagen (54K)

DON'T EVER try to charge through the high side. You could have the can blow up in your hand or blind you. All charging is done through the low (suction) side. High side is only for monitoring system performance. I'd advise wearing eye protection as well. If a line blows & the gas hits your eye it can freeze your eyeballs! Not trying to scare you, but a fully charged system can easily get over 200 psi, which can blow if there are any imperfections or weak spots in the system.
The fitting came from Johnstone Supply. They're nationwide & there's one in Tampa:

3650 W Spruce St
Tampa, FL 33607
(813) 875-4545

I had to open the ID slightly to fit over the tubing as it is not designed for this type of installation. Just regular solder & a small torch was used. No need to silver solder like you do for high pressure fittings, we're only dealing with vacuum. I don't think the top of a 134a can will work. The o ring in the hose end will not properly seal to a can top. It needs to have the proper taper & extension to seal or you'll loose a lot of vacuum. My fitting is for a R12 setup, but they have adapters that screw onto it to accomodate 134a gauge sets.

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K

You have several questions mixed together there.... but for educational purposes only... no one would condense to a tank and reuse without FILTERING it first... so at home with just the vacuum you would not want to do that even if you could...
On the condensing... I have heard of some home units... basically you put the R12 into a metal bottle made for that kind of activity... with Dry Ice packed around it when you are compressing it into there...
The way you find out if you have non condensible gases like air in there ( also for educational purposes... air is condensible ... but AC people call it that as tradition because they are talking about gases which are not condensible AT the temperatures and PRESSURES which the AC units are working at )...
is that you have a stick on thermometer on the side of the metal bottle.. I don't really understand it to the point I can explain it... but it is something like letting out some of the gases at the top of the container ( the ones that did not go to liquid , ie, non compressibles, out ... and checking the change in temperature of the gases and liquids in the metal bottle... but in letting some out you change the temperature automatically...so you have to wait for the whole thing to stabilize before doing it again.... When the expansion due to cooling is a certain way then you know you only have R12 or whatever in the metal bottle...
So anyway, if you were to follow the rules that close... condense to a metal bottle... there ARE places you could take it who would follow the rules further by testing what you brought...and cleaning it before selling it to others to hopefully continue the cycle.