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  #1  
Old 03-28-2003, 08:48 PM
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Location: Los Angeles, CA
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R134 conversion

My 82 300D Turbo was converted to R134 by the previous owner. I have owned the car for a few months and although the cooling capacity was subpar it functioned. The compressor and the expansion valve are leaking refrigerant oil. I added the UV tracer R134 to check for other leaks and found none. The AC does not cool anymore because enough freon has escaped thereby shutting down the compressor. I purchased a rebuilt AC compressor, new expansion valve and receiver/dryer.

I don't have the equipment to evacuate so I will bring it in to a local Pep Boys, etc to have it evacuated and charged once I instal the new parts. I will instal the receiver/dryer at the last moment so I minimise it's contamination with atmospheric moisture.

My question is should I clean out the system before putting on the new parts? How do I do this? FYI, I have an air compressor. Also what kind of oil should I put into the new components when I instal them. I have no idea about the oil type the last mechanic used when the system was switched to R134 or if he bothered flushing out the R12 oil so I'm concerned about compatability.
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  #2  
Old 03-29-2003, 08:13 AM
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R12

Try your best to go back to R12. It works the best and it's not that expensive. They'll do a test to see if the coolant is contaminated or mixed. Proper and correct amount of oil in a 134 system is very critical. You'll have to change the fittings back to the R12 fittings if the previous owner did a correct conversion.
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  #3  
Old 03-29-2003, 03:28 PM
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As long as your old compressor didn't blow up, I don't think you really need to flush the system. If you did want to flush the system, buy a blow gun that hooks to an air compressor and has a hose attachment that sucks up cleaner, and use mineral spirits. I've flushed two cars now and I would not recommend it if you don't really need to do it. Its a really sucky job. I did it because I was converting gases and therefore had to get all the old r12 mineral-based oil out.

As far as what kind of oil to use, I would talk to the people who sold you the compressor. Often a certain oil is required if you want to maintain the warranty on the component. BUT, if you are going to flush the system and make sure all the old oil is out, then the best oil to use is something called Texaco HFC. The guys at www.ackits.com will sell it to you, and they recommend it in all their applications. Talk to them about compatability if you don't flush the system. These guys are really knowledgable and friendly. They also sell flush fluid, the blow guns I was talking about, and just about everything else you need for a/c.

Read the following post for a happy-ending story to a r-134a conversion:

vent temps with r-134a w123

Good luck,

GregS
'84 300D, 173k
'90 300CE, 163k

P.S. If the r-134a conversion was done properly, there should be a blue sticker somewhere in the engine compartment, or on the compressor, indicating what kind of oil was used when the system was converted.
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  #4  
Old 03-29-2003, 05:48 PM
LarryBible
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Do yourself a favor and reverse convert to R12. The extra money for the R12 will be a small amount relative to all the other work and money you are putting into this project. The fittings are no problem, you will simply remove the R134 adapters.

You will, however, need to COMPLETELY flush the system. Because of the parts that you will replace, you will have most of the system apart and ready for flushing anyway.

Disconnect all the hoses and then remove the expansion valve. You can get a proper flush gun inexpensively at your auto a/c supply house. Simply open the cannister, pour in the flush agent. I prefer to use the flush agent that they sell specifically for this purpose, but mineral spirits will work.

Pour the flush agent in the cannister, put on the top and pressurize at the shrader valve on the cannister, then use the blow gun to force the flush agent through the evaporator, condensor and all hoses. Use compressed air TO THOROUGHLY REMOVE THE FLUSH AGENT! Do all this flushing and removal of flush agent BEFORE hooking up the hoses.

Once everything is flushed, use new o-rings everywhere and reassemble. When mounting the connection at the compressor, mount the manifold in place and make sure it is not cocked at an angle, before putting all the strain relief bolts in place for the hoses.

Use mineral oil. Ask your compressor supplier if the compressor already has oil and what kind it has. An R4 will probably have mineral oil and the correct amount BUT CHECK FOR SURE. The correct oil type and quantity are important.

Install your new filter drier LAST. Try to minimize the amount of time between installing the filter drier and evacuation, this way you will evacuate most of the moisture rather than loading up your new filter drier with it.

Make sure that the a/c technician that evacuates and charges KNOWS the situation about the system being completely opened and flushed. He needs to evacuate longer than you would under most circumstances.

Good luck,
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  #5  
Old 03-30-2003, 01:30 AM
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A mind heaping full of useless information.

Last semester in college I had thermodynamics where my professor (whom has a doctorate in mechanical engineering) said that R-134a (which was supposed to be the cure for the ozone problems) is simply not living up to its previous expectations. As you probably know, R-134a was never as good as R-12 in an A/C system, but now it really looks absurd because it is just as bad if not worse on the ozone than the freon it was supposed to replace, R-12. Go figure. And since I've enlightened you with one useless fact, here is another. The A/C system in your car is ~2X larger than the central A/C system in your house (rated in tonage).

The A/C in my 84 is very weak (all original), I think I'll add some more R-12 this summer. I shouldn't have to evacuate everything and start over, right?
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  #6  
Old 04-01-2003, 09:02 PM
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Location: Los Angeles, CA
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R134 oil, evacuation, gauge measurements

Thank you for the suggestions/advise I received from you all. I'm sure R12 would be the better solution if I was looking for max cooling. We live in west LA. It rarely hits 90 and the humidity is not too bad. As such we don't usually need the chilling capacity many other parts of the country need. For this reason I will not go through the additional expense and/or inconvenience of converting to R12. As a DIYer I prefer sticking with R134 since I don't have to depend as much on using a shop. My logic may be flawed but I will stay with R134.

Since my compressor did not catastrophically fail and i'm sticking with R134 I hope to avoid flushing. I plan on removing the receiver/dryer, expansion valve and compressor. Then I will use compressed air to blow out as much of the oil as possible out of the lines, condensor and evaporator without removing them. This way I am starting with an almost dry-of-oil system and I can then put 4 oz of oil into the suction side of the new compressor, 2 oz into the evaporator and 2 oz into the receiver/dryer. This will provide the 8oz total called for my system. If the oil that is dumped out of the compressor contains no particles I will assume that a flush is not absolutelty necessary. I will then install my new (not rebuilt) Four Seasons R4 compressor, new expansion valve and at the last moment a new receiver/dryer. I understand every connection should have a new blue or green o-ring that has been dipped in the PAG or Ester oil. I will then try to find a shop that will evacuate and charge unless someone can recommend an economical vacuum pump to do the evacuation. I don't need a recovery system since the system is almost empty of refrigerant.

The compressor maker ships the unit without oil and recommends PAG or Ester oil for R134 applications. They would not advise one over the other. Does anyone know which would be my better choice? The out of business shop that did the R134 conversion with the previous owner did not put a tag on the car stating which oil was used.

Also I was wondering if I should invest in a small vacuum pump so that I could evacuate myself instead of trying to schedule an expensive visit at a shop. Any recommendations on an economical vacuum pump (don't need recovery since the sysyem is almost empty of refrigerant). When filling the system do you fill based purely on the weight called for or do you use gauges. I would like to know the gauge value for checking after loading and on going checks. I heard a rule of thumb is (2 x F) + 20 = high side pressure and 30psi for the low side. I know humidity should be factored in but would this be close enough? MB has 300D A/C pressure curves for R12 but not for R134.
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  #7  
Old 04-01-2003, 11:22 PM
I told you so!
 
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You can make a vacuum pump from the pump motor of a discarded refrigerator or dehumidifier. Perfect for the DIYer.

All the reading I've done on aircondition.com tells me that it's worth the effort to mail order Texaco Capella HFC 100 synthetic refrigerant lubricant for your a/c system and nylog for the o-rings. To repeat Greg's link, you can get them at www.ackits.com
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  #8  
Old 04-01-2003, 11:45 PM
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Do not add refregerant according to weight. Period. Go strictly with gauge pressures - this IS important. You can purchase a set of gauges from ackits.com for around $50. When the compressor is running and the engine rpm is up around 1500-2000, you want the low side between 25 and 27psi. Don't go below 25psi, but get right down to it if you can. The high side will depend on the ambient air temperature (low side shouldn't). I can't remember exactly the high side pressure, but the ballpark is ambient temp. x 2.2. Generally you should be around 180psi to 190 psi, but remember that you will see both high and low side increase at idle (which is why you have to take the readings while someone brings up the rpm). At idle you may l see high side go to around 220psi.

I second the recommendation to use Nylog. This is highly recommended stuff - use it on all the o-rings and threads, and make sure to get the kind designed for 134a.

Again on the oil, talk to the guys at ackits.com. I'm pretty sure Ester is ONLY, ONLY supposed to be used if the system is completely new and free of old oil (whatever it may be). PAG is the conversion oil, but I know the Texaco stuff is supposed to be the best. You just need to check whether it is compatible with other oil.

Lastly, the evacuation (i.e. pulling a vaccum), is really important. Don't cut corners. You must get as much moisture out of the system as possible, which is what pulling a vacuum does. It also helps you check the system for leaks. 45 minutes is recommended at a minimum for a system the was just opened to do a repair. If the system was open for a long period of time, then you should pull it for maybe 1.5 hours. This is where your own pump is nice, because most shops probably won't pull the vacuum as long as they should.

8oz of oil is the right amount for a new system, but since you aren't flushing, and you may have some oil remaining in the hoses and condensor, you might want to cut out an ounce. Too much oil can reduce efficiency.

O.k., I've rambled on for long enough. I hope this helps. Ultimately, what I'm trying to stress is that it isn't that hard to fix the a/c systems on these cars to begin with, and as long as you are willing to do all this work, do yourself a favor, and get it right the first time around!

Lastly, be real careful installing the bolt that holds the manifold to the back of the compressor. This is an awkward job, and I nearly stripped the threads on my new compressor when I did it - ouch!

Good luck,

GregS
'84 300D, 173k
'90 300CE, 163k
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  #9  
Old 04-01-2003, 11:56 PM
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A word of caution here for those of us thinking about working on a/c:

-Never, ever try to add refregerant to the high side, ONLY the low side. The high side pressures get high enough to blow up the refrigerant can. Think what that might do to your hands and face.

-If you don't know which side is the high side and which is the low, they leave the repair to a professional.

-Refrigerant is to be added in gas form only. Do not turn the can upside down when you are adding the gas, which would cause liquid refrigerant to enter the system.

-Never try to use any heating element or torch, etc. to heat the can to get the refrigerant out. I read a case in lawschool where a mechanic used one of those old beverage heating elements to heat the water the refrigerant cans were in. He picked a can up and it blew up, taking his hand off.

-Wear safety goggles.

-Don't breath the gas if for some reason some comes out of the can or system in your presence.

GregS
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  #10  
Old 04-02-2003, 01:29 AM
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Location: Los Angeles, CA
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This is great! I'll have to print it. Appreciate the safety check list. The only daunting part is tracking down a trashed fridge and making a vacuum pump. I would have to go to one of the appliance junkyards arround here. The interest is there but not much time between my day job (prod. dev. Polymer Lithium batteries) and expanding family demands. Would have liked to rent one or buy a bench top vacuum pump like they sell for dry boxes, chem labs etc but they're probably too pricey as my budget would be arround $50.

I would think a predetermined mass of refrigerant would be accurate based on MB's conversion data between refrigerants. In any case I like the idea of using the gauges as it's a "window" into the system. If the condensor was changed (it looks pretty new) that could also affect the amount needed I would guess.

Thanks
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  #11  
Old 04-02-2003, 08:58 AM
LarryBible
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First of all if you want to do this job right use R12, you will be doing the same amount of work to do it right. You can go online and take a test for $15 for 609 certification that allows you to legally purchase R12.

Blowing out the lines with compressed air will accomplish nothing, in fact it will be a negative because you will be putting moisture in the lines that will be soaked up by the oil inside. You will have the lines broken anyway, so flush it with brake cleaner if you don't want to buy a flushing cannister. THEN BLOW THE FLUSHING AGENT OUT OF EVERYTHING COMPLETELY.

If you don't want to mess with an old refrigerator compressor, which would work very well by the way, you can buy a small vac pump from ackits or somewhere for about $200.

As said earlier ONLY use Ester oil in a converted system.

Good luck,
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  #12  
Old 04-02-2003, 01:38 PM
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The ultimate DIY vacuum pump

I have one of these and it works beautifully. All you need is a set of gauges (which you should have anyway) and a sufficiently beefy air compressor. No mechanical vacuum pump will get anywhere close to this price as well.

http://www.ntxtools.com/Merchant/merchant.mvc?Screen=PROD&Store_Code=01&Product_Code=ROB-34970&Category_Code=AC+Pumps
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  #13  
Old 04-02-2003, 02:57 PM
LarryBible
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I would definitely NOT recommend a venturi pump for the job that erubin will do. He will be flushing and blowing through the system with compressed air. The system will be PACKED with moisture. One of these will not pull a good enough vacuum for the SERIOUS evacuation that he will need.

I think it is worthwhile to point out here that the reason you are evacuating is to remove moisture. Moisture left in the system combines with the refrigerant to create an acid that will eat a hole in an aluminum evaporator in short order. R134 is even worse about this than is R12.

Good luck,
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  #14  
Old 04-02-2003, 05:37 PM
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Larry's absolutely right, you need a professional vacuum pump for this job. I would also agree that since you are going through all this trouble, you might as well get your certification and buy R12. R12 will work better, no question. I got decent results with r-134a, but a big factor, if you read my link, is because I custom fit a modern, parallel flow condensor. Since you are using the original style condensor, you should stick with R12.

I had such a monumental task ahead of me when I started my project (100% system rebuild with custom parts) that I didn't want to bother with the certification, but now I wish I had just so I could say the job was done absolutely as perfectly as could be, and have optimal cooling in city traffic. If you drive mostly highway then r-134a is o.k., but in city driving it really doesn't cut it.

GregS
'84 300D, 173k
'90 300CE, 163k
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  #15  
Old 04-02-2003, 09:04 PM
jack baker
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I must have been one of the lucky ones,,,,,converted to 134 and no problems,,,works terrific..at least it has for the last two seasons...jack
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