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  #1  
Old 04-01-2008, 04:11 PM
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Question Some help needed flushing and recharging my A/C

Im putting together the tools needed to do this hopefully in the next couple of weeks. I just installed a new evaporator. My system has not worked since I have had the car.

I am not replacing the compressor, but I do not know if it works or not. The whole system was converted to R134a 3/05 by PO, and has not been used since 3/06. Im hoping the compressor is OK.

my questions:

Do I need to remove the compressor to flush? Is there any way to make removing the compressor easier? It sounds like a real pain.

How big of an air compressor do I need to run the vacuum pump attachment thing that they rent at the autozone type places to evacuate the system to 29mmHg?

What type of oil do I need for R134a (I am keeping it with 134a)?

Thanks - I'm going to need some help to go this thing working since Ive never done AC work, but I'm looking forward to the learning. I think Ive already done the hardest part...

Thanks!
dd

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  #2  
Old 04-01-2008, 04:56 PM
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see the guide at www.dieselgiant.com

I did this last year on my 300D....followed the step by step guide at www.dieselgiant.com ; my AutoZone had a vacuum pump. The only use I had for compressed air was for the FLUSH and also the drying of the lines before I put everything back together. I have a small 8 gallon tank with a compressor that goes up to 120PSI.

As I recall....you can't get the compressor to engage until you charge the system.....but there may be a way to "trick" the compressor.

Good Luck.
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  #3  
Old 04-01-2008, 05:48 PM
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I'm also going to do a similar A/C job soon, a new parallel flow condenser, A/C flush, convert back to r-12 from r-134a. The compressor can't be power flushed... if it needs to be cleaned it must be removed, new oil poured in/out a many times, spinning the compressor by hand. Looks like a huge PITA to r/r the compressor and I'm not going to do it, it's a sumpless compressor so there shouldn't be much oil in there anyway. As for picking an oil, I wouldn't use PAG, since it's not compatible with r-12.. If you find r-134a doesn't cool good enough for Boston (it probably will be good though) then you can go back to r12, for $15 I got my EPA license from ase, $60 on eBay bought 2 12oz cans and 1 14oz can of freon. Synthetic compressor oil like BG frigiquiet2 seems to be good as well.
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  #4  
Old 04-01-2008, 06:10 PM
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Derburger,
I would suggest Castrol refrigeration oil--- Premium Mineral Lubrication for R12 Ac systems...
Cold flow 500 for R12....
You can count on the miscibility of the R12 to match this stuff.. the BG may or may not be as good... not much use taking a chance....
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  #5  
Old 04-01-2008, 06:47 PM
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Venturi effect vacuum generators have trouble drawing the max vacuum.
I made a nice vacuum pump out of a fridge compressor. Goes to 29.5 right quickly...

Jim
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  #6  
Old 04-01-2008, 06:47 PM
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Thank you for the replies.

So if my R-4 type compressor is sumpless, does that mean there will not be any oil and that I don't need to remove the compressor to do a flush? I know its a fine point but I want to be sure before I go disconnecting the thing.

I am hoping that with my squeaky clean evaporator and mild Boston climate (15-20 90 degree+ days a year) 134a will be sufficient. Ill switch later if its not enough...I want to get it working in any capacity first :-) Who knows, maybe I need a new condenser or compressor...I have no idea what their state is.


Other than the dieselgiant writeup, is there another good DIY out there someone knows of? What are the gotchyas of this process from those who have been down this road? I have the Haynes AC manual, but of couse its very general.

thanks,
dd
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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car
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  #7  
Old 04-01-2008, 06:53 PM
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R134a will work in a northern climate.

It's marginal here in Virginia when temps approach 100 degrees and the humidity is in the 90's. A "perfect" system will work, but a system that is not up to optimum will warm up when idling.

Install a new dryer whenever vacuuming and recharging, moisture in the system is your enemy. Vacuuming the system will only remove so much of the mositure, the dessicant will retain te moisture and inhibit max performance.

Jim
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  #8  
Old 04-01-2008, 07:33 PM
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While the A/C handy guys are reading this thread, will this O-ring kit fit the MB A/C system sizes? I think I've read other members using this kit. http://www.ackits.com/merchant.mvc?Screen=PROD&Store_Code=01&Product_Code=CP3025&Category_Code=vehiclespecific

Also, any suggestions as to good place to get a flush gun, and a gallon of solvent?
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  #9  
Old 04-01-2008, 07:35 PM
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The compressor really isn't that difficult to remove and replace. If you are going through the whole effort of replacing condenser and rec/dryer and maybe exp. vavle and flushing everything else, then removing the compressor and manually flushing it a bit I think would be worth the extra effort.
And it doesn't matter if it's R134a, Freeze12 or R12: when you are idling in heavy heat these systems warm back up. Sometimes almost 20 degrees if you really sit for a while.....
Possibly where the high flow aux fan could help.
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Old 04-01-2008, 08:03 PM
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Quote:
Originally Posted by derburger View Post

Also, any suggestions as to good place to get a flush gun, and a gallon of solvent?
You don't need a flush gun. I would not spend the money for a one-time use. Just use a small funnel and a hose to pour the solvent into the various componenets. And a half gallon of solvent will be more than enough.
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  #11  
Old 04-01-2008, 08:25 PM
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Seems to make more sense to put a refrigerant charge in the system first, maybe a couple of cans of 134a and see if the compressor works and whether or not there are any major leaks in the system, or other unforeseen problems. I just replaced the compressor, dryer, and expansion valve last spring, and found the a/c flush in a can worked pretty well, get two cans. Also used frigi-quiet synthetic oil, the compressor is virtually silent, the system cools well enough for NC as long as you're moving, and I just fired up the a/c for the first time this year and everything still works. Oh, and ******** AZ sells a complete o-ring kit for about $8. I also rigged the system for full recirc, which seems to help as well. Makes me happy that it isn't doing what it was originally designed to do anyway.
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  #12  
Old 04-02-2008, 12:14 AM
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Quote:
Originally Posted by ichbineinekrous View Post
Seems to make more sense to put a refrigerant charge in the system first, maybe a couple of cans of 134a and see if the compressor works and whether or not there are any major leaks in the system, or other unforeseen problems.
This makes sense to me to do. I have no idea what the status of my condenser or compressor are - they could be totally shot - and knowing my luck, they are . Should I add some oil as a precaution before pulling vac and charging?

JimmyL - thank you for the advice on R&Ring the compressor. Ill do it and not think twice. I never know how much a PITA something really is until I do it. Opinions definitely vary, but Iv read enough of your posts to know where your threshold is :-) I remember reading somewhere here that it was hard to get the 27mm socket on the crank bolt and a PITA....ummm no...

I will get the kit from ********AZ - thanks for the tip there. That sounds like 8 bucks well spent.


-dd
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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car
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  #13  
Old 04-02-2008, 10:33 AM
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To follow the rules you need to use nitrogen plus four ounces of R22 ... then check for leaks... you are then allowed to vent that to the atmosphere and either fix your leaks or install your refrigerant...
Notice that Jimmy was also smart enough to get a flush gun and several other AC type items... sometimes other factors... like safety come to mind when the actual practical work starts happening.... you can use a funnel and then a hand blow tip on compressed air to flush.. but your hands may be full of hoses ...and the positioning hard for gravity initial settup, etc.... and controlling the pressure.... sometimes there are REASONS that things like flush guns are produced... and often they are bought AFTER people have tried and found the lesser methods lacking in one factor or another.... controlling the input pressure with a hand held blowtip is different from setting up and using the flush gun... these are just things to think about.... but be sure during all ac work you have the goggles on....

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