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  #1  
Old 08-27-2010, 06:20 PM
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Need help with a/c recovery/recharge unit operation

Hello: I purchased an R134a/R12 dual refrigerant recovery and recharge unit. I just changed the a/c pressure switch and drier in my car. The machine pulled and held a vacuum on the system. So, all of that is fine. However, I can't get the freon into my a/c system.

I'm using R134a because it had already been converted. I just want the a/c working now and will convert back to R12 later. The problem now is the "pressurizing tank" light on the unit keeps flashing. The manual states that I should start the car and turn on the a/c because there is a pressure difference that needs to be corrected. I did that and it is still the same.

The a/c compressor in m car is not turning on because there is no refrigerant in the system. It seems like I'm almost there, but I need that little push from the in house experts.

Thank you for your help.
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  #2  
Old 08-27-2010, 11:20 PM
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I think I'm familiar with that unit. It will need to see 100PSI in the tank before it will charge. When it is "pressurizing tank" it is actually warming the tank which raises the pressure in the tank assuming it has sufficient refrigerant. It can take several minutes before pressure comes up. In addition there are valves inline and at the tank that need to be opened before use and ideally closed after every use. If the valves are closed it won't see the pressure and won't charge.
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  #3  
Old 08-28-2010, 07:24 AM
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Thanks for your response.

I pulled a vacuum on the car's a/c system and immediately set the unit to charge it with virgin R134. Seven ounces were sucked in rather quickly, then nothing. The virgin cylinder seemed to be heated pretty good. I don't know how hot it should get before the pressure is high enough. The manual says it could take 10 minutes, but it was longer than that.

The car's compressor doesn't seem to be turning on. The clutch certainly isn't turning, but I can turn it by hand. Does the car's compressor need to be running in order to draw in more of the refrigerant? If so, how do I get it to run?
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  #4  
Old 08-28-2010, 10:42 AM
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I vacuumed and tried to charge the system again. The low side reads 105 and the high side is 110. The compressor is still not on. Six ounces of refrigerant were sucked into the system before it stopped. Any ideas?
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  #5  
Old 08-28-2010, 10:48 AM
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search posts by larry bible.... he seems to know the systems...

there's a way to jump the a/c compressor to have it start up....
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  #6  
Old 08-28-2010, 10:52 AM
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from mb doc:

if you remove the klima & use a jumper wire between circuit 15(power) & 87(compressor) the compressor has to run....

Those circuits are marked on the relay..& are marked 5 & 7 on the electrical connector.

That test will allow you to decide if the compressor is good or if you are having "klima" control problems.
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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


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  #7  
Old 08-28-2010, 01:34 PM
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I had the same issue when I charged my 260E. It would not pull in anything more than the first can. In the end, I had to run the car at 2000rpm with the can in hot water for it do it. Have you tried that?

I am not sure why your low side is higher than the high side though. Possible blockage at expansion valve?

Did you put in correct amount of oil to correct for replacement of RD? (not your cause, but side Q)
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  #8  
Old 08-28-2010, 01:44 PM
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Quote:
Originally Posted by ps2cho View Post
I had the same issue when I charged my 260E. It would not pull in anything more than the first can. In the end, I had to run the car at 2000rpm with the can in hot water for it do it. Have you tried that?

I am not sure why your low side is higher than the high side though. Possible blockage at expansion valve?

Did you put in correct amount of oil to correct for replacement of RD? (not your cause, but side Q)
Thanks for your reply.

The a/c unit has a "blanket" which heats the virgin cylinder, so there's no issue with a can freezing. The cylinder is pretty well heated.

The low side pressure seems to be my problem right now. Before my system lost enough refrigerant for the compressor to shut of it was in good operating condition. Looking back at it now, there were moments when it was intermittent, but that was more than likely because the refrigerant was slowly being lost via the pressure switch.

Could the loss of freon have caused a problem wth the expansion valve?
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  #9  
Old 08-28-2010, 01:45 PM
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Yes, I replaced the oil.

Thank you.
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  #10  
Old 08-28-2010, 05:04 PM
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I'm going to keep throwings things out there until something sticks. So, can the drier be part of the problem? I started this whole process last evening. I put a new drier in at that time, but the system was not left under vacuum overnight. I haven't opened the system after that drier was installed, but hasn't it been accumulating moisture all of this time?

If I should change the drier again I will as I have another new one. If I have to pull a longer vacuum on the system before attempting to charge it again I can do that also.

I just need some ideas here.

Thank you.
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  #11  
Old 08-28-2010, 08:02 PM
LarryBible
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Recovery tank pressure is not what will keep it from charging from the tank. There is a float sensor in the tank and it will not release refrigerant from the tank until enough is in the tank for a charge. It will take several recoveries after tank preparation before you can charge from it.

Hope this helps.
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  #12  
Old 08-28-2010, 09:47 PM
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Thanks for your help.

However, I do not want to charge from the recovery tank. I want to charge from the virgin tank of R134. There's a mode selector button on the unit which lets me choose "Charge Virgin"... So, that's what I've been attempting to do.
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  #13  
Old 08-29-2010, 12:17 PM
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I went out this morning and pulled a vacuum on the system for an hour. Immediately after that hour was up I set the unit to charge the car's a/c system from the virgin tank of R134. This time it sucked in 1 pound of refrigerant. The low side pressure was 30 and the high was 200. The ambient temp was 85 degrees. The low pressure was actually all over the place at times. It went all the way up to 150 and dropped back down to between 30 and 40 rather quickly a number of times. I don't know if that's because of the pump going on and off or what.

If I shut the car off the low side goes to 70 and the high to 160. With the engine revving the low drops to 15 and the high up to 200. I can't get any more refrigerant in right now. I'm obviously getting there, but need that little push in the way of information as to what my next step should be.

The compressor turns on by itself now since there's a lb of R134 in the system. The vents blow cool, but not cold. I have to put 1 lb 6 oz more of refrigerant into the car.

Any help is appreciated.
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  #14  
Old 08-29-2010, 12:25 PM
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revving at 1500 ...you need to get in the upper 30's for low side...then you will have cool air... high side is almost there....

congratulations on the progress made.
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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


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  #15  
Old 08-29-2010, 12:29 PM
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Hey Lee: I had someone revving it up between 1500 and 2000 rpm. It just wouldn't draw in any more.
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