School me on my Renix AC system

Ok, so I have a 1990 XJ I picked up to drive while I recover from leg surgery (my DD is a manual, this XJ is an auto) and need to replace some AC components. It was in a front end wreck and the condenser was damaged and leaked out all the refrigerant. I have a condenser that's been sitting in my backyard for a few years now, exposed to the weather, which I am hoping I can use on this rig. Can I do that, and what do I have to do to prep it? I also was going to buy a new drier/accumulator and the expansion valve, assuming you all recommend it.

Question now is about the refrigerant. I found I can get R12 on Ebay relatively cheap if I'm EPA certified, research suggests the test is easy, so if I buy some R12 after getting certified how much do I need? Also, on previous rigs I had problems getting them to take in refrigerant when they were completely out for an unknown length of time, will I have the same problem trying to refill one which was known to work only a few months ago?

Thanks in advance!

P.S. I bought this rig with the intentions of reselling it later (unless I fall in love again and win the lottery...both of which are possible...right?) so I would love to do this 'right' but, really, I just need it to work for the next year or so if that's my only affordable option.

Most of my experience is with R134a; however R12 is similar and actually works better in a correctly operating system. You're right about the OSHA test for certification. It's pretty simple and doesn't require much; however you'll run in to trouble if you try to do this without the proper equipment. The cans of refrigerant you can buy in stores and online will not work because it's not the proper way to charge the system. You need to know what your high and low side pressures are to get a proper re-charge. Since your system has been open for an unknown amount of time, you'll need to also replace the receiver/dryer or accumulator when you replace the condenser and pull a deep vacuum on the system for at least 20 minutes. You'll need to find what type of PAG oil your compressor takes and inject the correct amount when you recharge on the low pressure side.

My advice....replace all parts and then take it somewhere to have it correctly charged. Being that it's an older R12 system you may have additional leaks elsewhere in the system like O-rings and fittings. When you get it charged correctly they can sniff for additional leaks so you don't waste new refrigerant.

R12 into the atmosphere = VERY BAD and highly illegal.

If you want it to work right you'll need a vacuum pump. Even that may not be enough, R-12 sucks up moisture, moisture in the expansion valve causes serious issues. One trip through the drier never removes all the moisture, the drier has a limit on how much moisture it can absorb.

The oil in the compressor is also likely polluted with moisture and whatever.

You can purge the system with dry Nitrogen before you pull your vacuum.

I'd dump as much of the oil as possible and replace it.

Adding Freon by weight and matching the FSM weight specification is the best way to fill. Contrary to popular belief more Freon doesn't mean more cold.

I usually fill (low pressure side) until it won't take anymore with the compressor off. Then I jump the compressor clutch directly to the battery watching my gauge. You want to avoid going below zero on the gauge in the beginning, though hopefully everything is sealed and it shouldn't cause any issues if it does go unto vacuum while you are filling. It can be a bit like juggling if you aren't familiar with the your gauges and valves, it takes some practice.

A littler trick you can use to get that last little bit out of the can is to sit the almost empty can in a pan of hot water. But be careful not to get any water on your fittings or hose ends, water/moisture is the enemy.

Since the system has been exposed to atmosphere, You will need to replace the receiver/drier. From my understanding, the Renix compressor will work fine with R134a.

Most points of this topic have been correctly answered with one exception.

To add to correct charge level pull a deep vacuum as mentioned and weigh in the correct amount of refrigerate as mentioned (in this case we can say FREON because it's R12)

Now the exception: Introduce the charge in liquid form (can upside down) through the HIGH SIDE.

If you have a true deep vacuum it will transfer the entire charge without starting the engine / compressor.

Weigh it in ACCURATELY in grams and if everything in the system is functioning properly all you need to do is disconnect the gauge set, install the caps on the high and low side fittings and drive away chillin !

dktool said:

Most points of this topic have been correctly answered with one exception.

To add to correct charge level pull a deep vacuum as mentioned and weigh in the correct amount of refrigerate as mentioned (in this case we can say FREON because it's R12)

Now the exception: Introduce the charge in liquid form (can upside down) through the HIGH SIDE.

If you have a true deep vacuum it will transfer the entire charge without starting the engine / compressor.

Weigh it in ACCURATELY in grams and if everything in the system is functioning properly all you need to do is disconnect the gauge set, install the caps on the high and low side fittings and drive away chillin !

Click to expand...

Only one problem with this method, how many grams does the hose hold? I guess you could heat the can and/or the hose and get enough pressure to move most of it. Slowly feeding gas into the low side, with the compressor running, is likely to get more Freon were you want it, inside the system.

Be careful not to burn your fingers when disconnecting the hose if you fill liquid. Gravity feeds can be iffy.

DKTools method my work out for you, not the way I learned it.

Awesome stuff guys, thanks! Really appreciate the concise replies. I'll try and go through the FSM next time I'm able to hobble to where I stashed it and hopefully everything else will be straight forward from there. Just wanted to confirm the basics before I go ordering things.

Just to clarify though, is there anything I need to do to prep the condenser I plan to reuse? I dumped some water out of it a few days ago and have since left it in the sun with the hoses down. It sat outside for anywhere from a year to three years, I'm not exactly sure which rig it's off of. I don't want to have the condenser give me any problems.

Because literally being a few weeks out of surgery makes working on a car by yourself a pain in the arse...and I need to fix this car so I can get myself where I need to be. Unfortunately, where I need to be is going to be 100 degrees regularly too.

dktool said:

Now the exception: Introduce the charge in liquid form (can upside down) through the HIGH SIDE.

Click to expand...

This is completely wrong and dangerous. Never, never charge an AC system on the high pressure side if possible. The high pressure side can cause serious injury to the operator if they're unfamiliar with pressures and temperatures. Most "snake oil" AC fixes have fittings only for the low side because of this. This is basic AC 101.

98NWCherokee said:

This is completely wrong and dangerous. Never, never charge an AC system on the high pressure side if possible. The high pressure side can cause serious injury to the operator if they're unfamiliar with pressures and temperatures. Most "snake oil" AC fixes have fittings only for the low side because of this. This is basic AC 101.

Click to expand...

He is charging without the engine running.

old_man said:

He is charging without the engine running.

Click to expand...

Usually filling a stopped compressor and the system stops taking Freon at a round 60 PSI (depending on the ambient temperature and the temperature of the can/bottle). Even gravity feeding the system (holding the can above the system and letting gravity flow the liquid) the pressures inside the can and in the system are going to try and equalize.

I've never tried it this way so I can't say for sure how it may work out for you. I can see a few issues that might pop up. The liquid being fed into the high side is going to fill the high side tubing pretty quickly, start to boil and build pressure. The expansion valve is going to be a bottle neck. The pressure rise from the expanding gas is going to slow the liquid feed. In an automotive system the compressor is most of your accumulation capacity, The accumulator drier isn't nearly big enough to hold all the Freon.

I've liquid filled systems before, but commercial sized systems with a large accumulator and never succeeded a complete fill this way.

IMO a lot safer dealing with the gas than the liquid. Remember you have five valves to deal with, two on your manifold, two on the compressor and one on the can. Plus two gauges and the pressure in the hoses. Not a particularly overly complicated combination of tasks, but it can get confusing fast (kind of like a monkey fornicating with a football).

I've never taught refrigeration, I did it for a living nearly half a century. Mostly commercial type systems and not automotive. I imagine there are some tricks to automotive refrigeration I never learned.

Muddy Beast said:

Just to clarify though, is there anything I need to do to prep the condenser I plan to reuse? I dumped some water out of it a few days ago and have since left it in the sun with the hoses down. It sat outside for anywhere from a year to three years, I'm not exactly sure which rig it's off of. I don't want to have the condenser give me any problems.

Click to expand...

*cough*

I'm sure the experts are going to cry foul, but look into 152 as a refrigerant.

I know everyone is all "butane in the system!!!"

I'm more concerned with the 60PSI fuel rail and the 18 gallons of gasoline behind my seat than 10 oz of butane in my AC system.

I'll be filling mine with computer duster.

Muddy Beast said:

*cough*

Click to expand...

Blow it out with air, wash it out with solvent, blow it out with air again. Look in the end opening with a flashlight, see if it looks like it is scaling or covered in green. If it is scaling not much hope for it, the scales will flake off and eventually plug the expansion valve screen. The green tuff can be removed with acid, sulfamic or something similar.

Scaling is another reason not to add liquid Freon when filling, it can freeze dry the metal and cause scaling.

I don't know which type of solvent to recommend, we used to use a fluorocarbon solvent that was compatible with Freon 12, it is forbidden now. Carbon tetra-chloride might be OK, also hard to come by anymore. Just an opinion, but most any solvent that will dry (evaporate) completely (Ether?) and remove the left over oil will likely be OK, just avoid the fumes. But I'm not a chemist and using non approved solvents around F-12 can produce Fluorine gas, which will kill you. There is always some trapped F-12 in old refrigerant oil. A good question for EcoMike.

http://www.teamec.be/cms_files/Flushing and Cleaning(EN).pdf

Any refrigeration supply place will have a flushing agent compatible with R-12. I'm thinking it may be overkill for a small system like an auto A/C, but may be a lot safer than guessing.

What you really have to hope for is to get all the moisture out and hope the expansion valve screen doesn't get plugged. the filter drier should collect most of the solids, hopefully. Whatever particles that are in the system after the filter drier, the expansion valve screen will catch. If the screen gets plugged your screwed, if sufficient moisture makes it to the expansion valve you are also likely screwed and can start the process all over again.

My opinion on using non approved solvent to clean the oil and trash out of the tubing on a condenser, was just for the condenser and not for the whole system. The wrong solvent, some air and 200+PSI, equals boom.