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1970's GM A/C Receiver/Dryer Help Desperately Needed

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Hello,

   I have a 1974 Camaro with the original-style A/C system.  It was trashed when I bought the car years ago and I had it converted to R134A when I did the restoration about 7 years ago.  As many of the original components were used as possible.  Since then, the A/C system worked great, but always had oil leaking from the front of the compressor and spraying all over the engine bay.  I just replaced the front seal on the compressor myself with a modern double-lipped seal, so I'm hoping for the best with no more leaks.

 

  During this seal replacement, the system was exposed to outside air for while, so I need to do something about the receiver/dryer.  I'm no A/C guy by any stretch, so I'm not sure what to do to either put new desiccant in it or just replace the whole thing.  Photo 1 is the  whole VIR / Receiver/Dryer System that I took off the car.  The green mess is dye put in to track the original leaks.  I want to keep the original components intact, so I wanted to ask the following questions to the group:

 

1) Can I just replace the desiccant bags (photo 2)?  I had Classic Auto Air restore this system originally, so at one point, they replaced the desiccant bags, so I know it can be done.  If so, does anyone know where I can get them and how I install them without ruining them by exposing them to the air?  If I can do this, is there anything else that should be fixed/replaced, other than maybe the O-rings?

 

2) I've had a few friends and forums I've read on other sites tell me to just replace the receiver/dryer, but all the ones I see are modern replacements and do not look anything close to mine, so that doesn't seem like a good solution, but maybe I'm missing something?  I haven't been able to find this component online anywhere (Part #1131047).

 

Any help or advice is greatly appreciated, as this has been a very frustrating and expensive experience of just trying to get my A/C to work properly.  Thanks!!!

 

-Chris

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Desiccant is re-useable. Just heat it up to change the color. Usually clearish beige/pink means wet and dark blue means dry and ready to use.

 

I used a desiccant dryer in the paint booth for many years. Held about 500 cubic inches of desiccant. Waaayyy too much to buy every time it got wet. So, I put it in batches on a paper plate into the shop microwave!

 

It is the filter that might get clogged and make it perform poorly. 

 

An OLD used car trick is to apply vacuum to the A/C system and put a heat lamp on the receiver/dryer to make the desiccant return to the dry state! Why replace parts to sell a car with working A/C?;)

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I grew up in a family full of car dealers and Frank knows his old used car tricks. As you already have your dryer open, might as well give those two bags a couple minutes in the nuke. Don't do it while the wife is home, clean inside the microwave and scrub up the kitchen from end to end with Lysol to cover the short term smell when you're done and she'll think you're a hero.

 

Putting the AC back together the right way always means sucking a vacuum and making sure it doesn't leak. Your desiccant bags still look kind of blue, vacuum pulls moisture from the system, short term exposure to air isn't enough to soak the desiccant to the point where vacuum won't dry it, but you already have it open so you might as well give it the full nine yards. 

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Thanks for the tips, but I guess I don't really understand how the system works to being with, plus my desiccant bags are an oily mess, so I'm not sure if re-heating them would even work.  I wouldn't be able to tell if they are fully dry or not, either.  The things I don't understand, and can't find a good explanation of how they actually work, are:

 

1) Does the receptacle where the desiccant bags are located hold enough oil/liquid refrigerant to cover the desiccant bags when in normal use, or is it just a small amount at the bottom?  My desiccant bags are soaked in oil and are green in color, not blue, from dye, so I can't use color as a determinant of dryness.

 

2) It appears that replacing the desiccant bags (or heating them up) is a viable option, but how are the desiccant bags protected from moisture to begin with?  Let's say I order new desiccant bags.  I assume they would come in a vacuum-sealed bag.  When I take them out of the bag, is the amount of time it takes to put them in the canister, and hook the receiver/dryer back up a small enough time that I don't have to worry about it absorbing much moisture?  What about when the system is all sealed up again, there was outside air in the system, so is this just a tolerable amount?  How long can I wait before I get the system charged?  Like you mention, I need to draw a vacuum, but I don't have the equipment or knowledge to do that, I'd take it to a shop to pull vacuum and have the system re-charged.

 

3) Do I need to put oil in the receiver/dryer canister with the desiccant bags?  One youtube video mentions that, but I don't know what the truth is, or how much, if any, to put in.

 

As you can tell, I'm learning about A/C, but overall very clueless and I don't really understand it.  Thanks again.

 

-Chris

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If my memory serves me correctly: Water boils at 40 degrees F. under a 26 inch vacuum.

Therefore you can put your ac system together and pull a maximum  vacuum on it for about 30 minutes and be home safe.

Your maximum vacuum will depend an your altitude.

(That is 50 yrs. shop experience talking.)

 

 

Enjoy, Bill

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1 hour ago, Willie Wurke said:

If my memory serves me correctly: Water boils at 40 degrees F. under a 26 inch vacuum.

Therefore you can put your ac system together and pull a maximum  vacuum on it for about 30 minutes and be home safe.

Your maximum vacuum will depend an your altitude.

(That is 50 yrs. shop experience talking.)

 

 

Enjoy, Bill

 

I agree. Pulling a  vacuum for at least 30 minutes is part of the a/c service procedure.  If you are really concerned, just leave it on for 1 hour.  Should suck out all of the moisture.

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Chris,

Desiccant works like a sponge and it's packed and shipped with about the same amount of care as the four pack of sponges you buy at the dollar store. Like a sponge it only holds so much moisture before it won't hold any more and it's entire job is to suck up any moisture left in the line when the system is charged. Absolute dry isn't absolutely necessary, it just needs to be dry enough.

To lubricate the pump you add oil to the charge and some oil always settles into low spots when not in use.  Like a water separator on an air hose doesn't remove all water moisture, the line filters in the AC system keep oil from moving in volume to places where you don't want large drops to go, but an oily mist is always moving through. If the bags weren't a bit oily after use things aren't working as expected.

The green leak detect dye will never come out of the bag and it's the oil from the AC system that stinks up the kitchen when you heat these things up. With your own tools and time, pulling a vacuum long enough can dry out a system that is a bit wet, putting a heat lamp on the dryer while sucking vacuum cuts down the amount of time to get that job done. When they are soaked to the gills you replace the dryer because you will probably fry your vacuum pump before that job gets done. You have a factory original dryer that was made to be serviced, you lucky dog,

 

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Thank you again for the replies, but don't have the tools, knowledge, or equipment to pull a vacuum on the system, and that is not something I'm concerned with yet.

 

I really appreciate the responses, but none of the responses actually address the specific questions I have, which are:

 

1) Does the receptacle where the desiccant bags are located hold enough oil/liquid refrigerant to cover the desiccant bags when in normal use, or is it just a small amount at the bottom?  I understand oil is in there, but I don't understand how much.  My desiccant bags are soaked in oil and are green in color, not blue, from dye, so I can't use color as a determinant of dryness.  I don't care if they are dyed green or not.

 

2) It appears that replacing the desiccant bags (or heating them up) is a viable option, but how are the desiccant bags protected from moisture to begin with?  Let's say I order new desiccant bags, or, dry out the old bags.  When I take them out of the bag (if new) or out of the microwave, is the amount of time it takes to put them in the canister, and hook the receiver/dryer back up a small enough time that I don't have to worry about it absorbing much moisture?  What about when the system is all sealed up again, there was outside air in the system, so is this just a tolerable amount?  How long can I wait before I get the system charged?  Like you mention, I need to draw a vacuum, but I don't have the equipment or knowledge to do that, I'd take it to a shop to pull vacuum and have the system re-charged.  Vacuum is not an issue at the moment.

 

3) Do I need to put oil in the receiver/dryer canister with the desiccant bags?  One youtube video mentions that, but I don't know what the truth is, or how much, if any, to put in.  How much oil is put into desiccant bag receptacle?  What type of oil?

 

Can anyone address these specific questions? 

 

Thanks again.

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1 hour ago, Ben Bruce aka First Born said:

 

A thought. Probably should know this at my advanced age. Can one pull a vacuum using the car engine?

 

  Ben

 

Not enough. Engine vacuum is at best about 20 inches.  Would normally be in the 14-16 inches of vacuum.

 

To answer the earlier questions,

 

1.  The receiver dryer does not fill with oil.  If you have too much oil in the system you can damage the compressor.

 

2. I have not bought any bags, but I would guess that they would come in a "zip lock" or other similar sealed package.  They do not instantly absorb moisture.  It takes some time.   Vacuum is an issue as if there is moisture in the system it could damage the compressor or other components in the system.  If you do not have the tools, then take it to a shop and have them evacuate and recharge the system.  Ideally once the system is evacuated and recharged you would have minimal moisture in the system and that is what the desiccant bags are for.   What ever you do, DO NOT let the system stand open.  Bad move.

 

3. With the system being an R-12 system originally I would drain all of the oil out of the system.  I would then take it to a shop to have them evacuate and recharge the system.  TELL THEM that the system has been open and all of the oil in the receiver dryer has been emptied and the system needs oil added to the system.

 

If they do it correctly and the rest of the system is good, you should be good.  If the system has sat open then it is a crap shoot.

 

Good luck.

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Thank you Larry, this is more helpful to my specific questions.  I think I have a little better understanding now.  I think I will just buy some new desiccant bags and start fresh.  I'll clean all the oil remnants out of the receiver/dryer, then I will then button it up and take it to my mechanic who has the proper equipment.  I've taken it to him before for evacuating and charging, as this is about the 4th time I've been through this process, so I'm sure that will go well. One of the hoses had a plug that I put in fall out, so the system has been open, possibly for a while, but without the compressor on the car, so I'm in the crap shoot phase.  I've plugged everything else up now that the receiver/dryer is out of the car.  Poor due diligence on my part, but I guess that's how you learn.

 

Thanks again to everyone that posted, I do appreciate everyone's responses.

 

-Chris

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Yes, the receiver/dryer (VIR) should not fill with oil. just a mist should go through, coating everything, but not filling the reservoir up. The name "Receiver" is to hold Freon (refrigerant), not oil. Freon is a solvent, therefore it carries the oil around the system when it runs (also why old timers said to run the AC even in the winter on a regular basis to circulate the oil).

 

Yes, engine vacuum no where near low enough (high enough?) to vacuum an AC system. The vacuum pump should be able to pull the system down to 500 Torr, or, say the vacuum gauge should get real close to the day's barometric pressure reading! For many years I used a compressor out of a thrown away refrigerator as my vacuum pump. Now I have a "real one" with the oil reservoir for AC work. 

 

I vacuum at least 30 minutes, then stop vacuuming and see if the pressure rises. It can rise form a leak, or water evaporating. Then I vacuum it again. If not in a hurry, I leave the system under vacuum overnight just to see how the gauge changes. Then I vacuum it another 30 minutes the next day and, if OK, suck the proper weight of refrigerant into the system. Sure this might be overkill, but it gets the desiccant really dry! Proper Freon weight, good, proper oil amount, good, water in any form (air), bad,  will cause problems, from uncompressability to rust/corrosion! Oh, or water drop forming at the expansion valve, freezing, and blocking the flow of refrigerant.

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Because of the low pressure switch, generally speaking a/c systems will run down to about 40deg F. 

 

It is run when the defroster is turned on to help make sure that any moisture in the air is removed and not deposited on the windshield.

 

11 hours ago, Frank DuVal said:

 

I vacuum at least 30 minutes, then stop vacuuming and see if the pressure rises. It can rise form a leak, or water evaporating. Then I vacuum it again. If not in a hurry, I leave the system under vacuum overnight just to see how the gauge changes. Then I vacuum it another 30 minutes the next day and, if OK, suck the proper weight of refrigerant into the system.

 

I do the same.

Edited by Larry Schramm (see edit history)

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Chris,

 

The above information is basicly spot on. I have worked in the industrial refrigeration industry for 25+ years. The desicant bags can be dryed with a microvave oven or better yet, in the regular oven set to about 180 degrees overnight. Both ways work, but the oven just seems more right to eveporate moisture.  To address your questions. The reciever/dryer is not FULL of anything in normal operation, however it will have some oil and liquid refrigerant in it when things are right and working. My approach to your problem would be to talk with your mechanic and see what his approach would be. The new desicant bags should be shipped in an airtight package. If in question just dry the new bags as above before you install them. Now for something that has not been mentioned yet... There are cleaner/solvents that are specific to cleaning freon refrigeration systems. They are poured into the system and then flushed through with air, or better, nitrogen. This will clear any old oil and dust etc...  After that is done the system is assembled with new orings and seals everywhere and vacuum is applied. If your mechanic will accomidate you, I would ask him/her to keep the system under vacuum for at least 24 hours. More is always better and it will assure a dry system. Next is to charge with refrigerant AND oil to the proper levels/amounts/poundage etc as stated in the manual. At that time you should be in great shape to enjoy a cool ride on a hot day. Your best friend in this case is a GOOD AC mechanic that will listen to you and that you trust. Oh yea, your other question about the desicant bags... Make sure they are dry and put them in last. They will be fine out in the open for hours/days unless it is in a rain storm.  No oil in the reviever/dryer unless specificly stated in the service manual. The oil is for the compressor and it will be carried through the system as a vapor with the refrigerant.

 

Edited by 37_Roadmaster_C
spelling (see edit history)
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In order to pull a vacuum, Ages ago I once used an old refrigerator's guts and soldered on the fittings to adapt the A/C hoses.

Once I pulled a vacuum for 24 hours, left it for another 48 hours just to test the system before refilling with R-12 which had become very expensive.

I bought out a big supply of R-12 in 12 oz cans at $30/can to be able to service my (then) five different card which had A/C.

Since I no longer have any of those cars, I would be willing to help anyone who wishes to use R-12, rather than converting to R-134A which is less effective in our older systems, even with the adapters.

 

PM me if I can help you.

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Thanks again for all the input.  I have a much better understanding of what's going on now.  I think I will try drying out the existing desiccant bags, as I cannot find reasonably-sized new replacements. However, I'll have to wait for quite a while, as we have snow coming in, which means salt on the roads, which means the car will have to sit for a while until the roads are clean enough to drive the car to my mechanic.  My mechanic is not an A/C guy.  There are no A/C shops anywhere near the DC area, so I have to do the best I can with my own weak knowledge and the advice of folks like yourselves.  I'll provide an update once I'm able to get everything back together.  Thanks again for all the knowledge.

 

My A/C worked great with the  R134A, but my compressor always leaked oil, hence the reason the A/C system is apart.  I'm hoping my switch to a modern double-lipped seal will repair the oil leak issue once and for all.

 

Thank you!

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