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AC system: R12 or R134A


iceman69510 Galant VR4.org Moderator
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Galant VR-4 org Post #: 346493 posted 06/05/06 11:19 AM     Remind Me!  Send Private Message   Edit Post      
I am almost to the stage of re assembling the AC system on 115. Any thoughts on whether I should recharge with R12 or change over to 134? I will need vacuuming of the system to check for leaks (system was apart and off the car) and to pull out moisture, so I will probably take it somewhere. Pay for the 12 and be done? Or convert and have it cheaper to work on later?

Sources for conversion kits appreciated as well.



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Galant VR-4 org Post #: 346497 posted 06/05/06 11:26 AM     Remind Me!  Send Private Message   Edit Post      
The conversion kits are about $35.00 for any parts store. Get the kit that comes with 2 cans of 134A and the fill hose. Replace the exspantion valve and dryer, then take it to a service center to have it vacumned down. Once it is at neg pressure, fill it yourself with 134A.

Super simple.



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Galant VR-4 org Post #: 346514 posted 06/05/06 12:15 PM     Remind Me!  Send Private Message   Edit Post      
Is the negative pressure part necessary? We bled mine before the engine came out, and I have yet to fill it. I've got a big bottle of 134a with a gauge and hose from AutoZone. I was under the impression that all I had to do was screw in the hose (already converted to 134a a few years ago) and empty the bottle



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iceman69510 Galant VR4.org Moderator
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Galant VR-4 org Post #: 346528 posted 06/05/06 12:40 PM     Remind Me!  Send Private Message   Edit Post      
Is there a way to know for certain I SHOULD replace the dryer, or just a good precautionary idea.

I want to vacuum test mine because it has all been apart and I replaced most of the orings. Want to make sure it all works before I fill it.



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Galant VR-4 org Post #: 346541 posted 06/05/06 01:31 PM     Remind Me!  Send Private Message   Edit Post      
all i did was bought the kit, changed the valves and added three 12 oz cans of 134. its nice and cool with no problems.Also, i think there is a special can of compressor oil you should put to oil the compressor so it doesnt seize.

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ken inn
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Galant VR-4 org Post #: 346576 posted 06/05/06 02:38 PM     Remind Me!  Send Private Message   Edit Post      
Quote:

Is there a way to know for certain I SHOULD replace the dryer, or just a good precautionary idea.

I want to vacuum test mine because it has all been apart and I replaced most of the orings. Want to make sure it all works before I fill it.




if your system has been open to atmosphere for more than 30 minutes, you need a drier. also, 134a is very sensitive to moisture. for that reason alone, i would put a drier. aftermarket driers are only about 10 bucks. 134a hit the roof last summer, it has come down a lot since then. vacuuming the system is essential to check for leaks. also, vacuuming will remove most of the moisture. if you dont or cant vacuum the system, go with an aftermarket refrig like envirosafe



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Galant VR-4 org Post #: 346608 posted 06/05/06 03:36 PM     Remind Me!  Send Private Message   Edit Post      
Since you mentioned you have broken the integrity of the system I would highly recommend having it vacuumed down(for approximately 15 minutes) then testing that the system keeps the same vacuum for at least 5 minutes. Pulling a high vacuum forces any residual water vapor to boil off. It is also used to see of the system is sealed.

You always want to replace your old drier canister if you have had it apart for any length of time. Most desiccant driers are long gone at 15 years old. They can only absorm approximately 1/2 tablespoon or water when new.

Although you might be tempted to use R12 the problem is that if everything is not perfect(seals, bad compressor, expansion valve, drier) the first time then you have to remove that R12 since your not really supposed to vent it to atmosphere. The second reason for pulling a vacuum is to test for leaks. At $9 per can that can get expensive if it leaks out.

If you replaced any part in the AC go in the service manual. There is a list of amounts of oil by part replaced that you should add back to the system. A new or rebuilt compressor comes shipped with oil. If you are converting an old system, most of the oil is likely leaked out. Some oil is always present in the system.

Mineral oil is not mixable with R134a and the old oil contains traces of R12 refrigerant which will react with R134a. Removing the compressor and draining the oil(usually about a 1/6 cup) helps. It won't kill a system not to do it but the oils PAG(polyalkyl glycol) and (POE) Poly Ester are displaced by the old oil. Some compressors can starve for oil because of this, even then oil is added.

The recommended procedure is to use brake parts cleaner (not carburetor cleaner and not the environmentally friendly brake parts cleaner), to blow into the lines, then use an air compressor to blow through each section. Put your thumb on the the exit, let it build pressure then release and let it blow out. This serves several purposes. It removes most, if not all residual oils, contaminants, and any metal particles if you had a blown compressor. Second, the brake parts cleaner evaporates quickly leaving zero residue. The particular section you want to do this with is the condenser and lines. I would stay away from doing the evaporator unless your changing the expansion valve.

Watch your paint, wear safety glasses, brake parts cleaner is dangerous. Oh, and its flammable with an octane rating of like 110.

Blowing out your lines is optional. Shops use a liquid flush and usually only if your looking.

Any section you blow out add back the proper amount of oil. Try not to exceed the maximum per the shop manual. The total for the compressor is "the" total amount for the system, not total added in addition to the other parts. when you blow out a part you are subtracting from the total the compressor came shipped with, which eventually gets distributed throughout the system.

You can pour oil right in the front fitting, then let it settle.

Adding refrigerant is simple, the low side line is on the top of the compressor. Do not shake nor turn the can over. You do not want liquid refrigerant, only gaseous (think hydraulic lock in a piston). Screw it down, make sure the valve is closed, puncture and open the valve. The compressor will not cut on until the system has over 30psi. Once the first can is opened and refrigerant is flowing(the can ices) the system will be at about 40 to 50 psi. Without undoing the connection start the car and set the idle at about 1500RPM. Kick on the AC(green). The compressor will start lowering the low side pressure(to approx 30PSI) allowing some of the remaining refrigerant to be pulled from the can. If you want to squeeze a little more out of the can, put the can in a pan of almost hot water(that will get you to 60PSI+ on the first can). Remember though that the running AC belt is right under the fitting.

Close the valve, undo and vent the can (watch out). Put on a second can and repeat the process. By this time you should be starting to feel the cooling. Part of a third can should have it cold. One line going in the back of the firewall should be cold, the other hot.

If you have a temp meter you can keep an eye on the temperature. The coldest you should be able to get it is 38 degrees. In reality I was only able to get as low as 54 degrees. As many times as I had to break it loose I may have tiny amount of water in the system or a bit too much oil, or a bit of air.

Its better to go have a shop charge it initially. A decent vacuum pump costs around $200. The harbor freight air compressor driven venturi pumps are not adequate for pulling a high enough vacuum to lower the boiling point of water to your climate temperatures. Proper gauges run about $75 plus miscellaneous fittings. There is also some who believe the larger 30lb canisters are better to charge from since you don't introduce the tiny amount of air and moisture from switching cans.

Be weary of some of the end all be all replacement kits. Be weary of the "hybrid" mixes that magically allow existing R12 to work with R134a. They are not considered compatible refrigerants. It depends on how good of shape your existing system is in when you do the conversion. Just changing to R134a it is recommended O-rings be replaced since R134a is a smaller molecule.


Edited by s_firestone (06/05/06 03:41 PM)

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spoulson
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Galant VR-4 org Post #: 346893 posted 06/06/06 09:32 AM     Remind Me!  Send Private Message   Edit Post      
I've been able to locate these O-rings on CAPS:
3x MB276213 O-RING,A/C PIPING 8 (incl. 2)
1x MB276214 O-RING,A/C PIPING 1/2" (incl. 2)
1x MB276215 O-RING,A/C PIPING 5/8" (incl. 2)

I've been advised to also add UV dye to the charge for future troubleshooting of leaks.

So, is it still worth the effort of trying to get R12 back into our cars? Searching eBay still picks up some sales for about $10-15/can.

As I understand it, even properly installed, R134a isn't as efficient a refrigerant when installed in a system designed for R12.



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Galant VR-4 org Post #: 346970 posted 06/06/06 12:24 PM     Remind Me!  Send Private Message   Edit Post      
i have a question about dryers. if its nearly brand new and has set with the lines open for a while, its dead and needs a new dryer correct?

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iceman69510 Galant VR4.org Moderator
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Galant VR-4 org Post #: 347084 posted 06/06/06 03:43 PM     Remind Me!  Send Private Message   Edit Post      
Found a new dryer today. The local AC shop will order it. $27, while Mitsu wants about $100. Now I have to decide to convert to R134 or not. $55/lb they want for r12 fill, $18/lb for R134. Plus labor to suck down etc. R134 conversion is another $150 if they do it. I have 2 cans of that dangerous R12 in my garage. If I can get them to use that, maybe I can get away cheap.



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s_firestone
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Galant VR-4 org Post #: 347146 posted 06/06/06 05:49 PM     Remind Me!  Send Private Message   Edit Post      
Quote:

i have a question about dryers. if its nearly brand new and has set with the lines open for a while, its dead and needs a new dryer correct?




The capacity of the opened one will be diminished if not used up. It's a dessicant package similar to a diaper.

I had to break mine open several times after replacing the dryer. Yes it still works but it may be diminishing my AC's capacity.

Heres how water vapor in the AC reacts.

A droplet of water hits the compressor with the refrigerant. It travels to the condenser under extreme pressure. When the refrigerant passes through the condenser is cools and the pressure drops. The droplet of water becomes an ice crystal instantly. This ice crystal moves along the cold side until it hits the expansion valve orfice at the evaporator. Since it's solid it retricts the expansion valve. An expansion valve is a hydraulically operated thermostat that regulates coolant flow speed. The ice crystal wedges in the opening and no coolant can flow. The evaporator begins to warm (as does your air). The ice crystal melts and is no longer a restriction. The evaporator begins cooling (and so does your air). The ice is now a water droplet again and the process repeats. Back to the compressor.

Add a drier and that water droplets get removed from the system. Steady coolant flow regulated only by the expansion valve to inhibit freezing of the evaporator. A full or bad drier is like no drier. If you get lucky and have zero water in the system then your Ok. But it is a given since water is always present in air and even the small amount of air in the charge hose connecting a can of refrigerant is enough to cause a problem.



Stephen Firestone
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Galant VR-4 org Post #: 347527 posted 06/07/06 03:09 PM     Remind Me!  Send Private Message   Edit Post      
cool thanks allot^^^. my brothers car has been sitting with the ac system open for a while due to unrelenting engine trouble and its a fairly new car, so it would be a shame to have the AC system not work.

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DSMTurbo2
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Galant VR-4 org Post #: 348460 posted 06/10/06 12:19 PM     Remind Me!  Send Private Message   Edit Post      
Im fairly confident that TELs have a sight piece in one of the lines that again i recall was an indicator of the pressure in the system. Do we have anything like that on our GVR4's or am I completly wrong all together?

My problem was simply that my ac belt was removed when i got my car. none of the system is open and i was wondering if there was an easy way to if the system still has pressure, or maybe is even still fine and ideally just needs a belt (yeah right). could i check voltage at the low pressure switch or something? thanks. Erik



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spoulson
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Galant VR-4 org Post #: 348558 posted 06/10/06 08:40 PM     Remind Me!  Send Private Message   Edit Post      
You'd need a pressure gauge for your AC system. Most parts places will have them, but you want to make sure it fits R12 systems; assuming you haven't been converted to R134a.



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Galant VR-4 org Post #: 348586 posted 06/10/06 11:48 PM     Remind Me!  Send Private Message   Edit Post      
I see.. am i wrong in understanding about there being a low pressure switch in the system? I was really just looking for a simple yes or no on if I should go buy a belt and give it a whirl.. im really not to upset with not having ac.. but i dont want to remove it either. so if it works then i guess i would like to use it. if that makes any sense



Erik O.

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s_firestone
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Galant VR-4 org Post #: 348611 posted 06/11/06 07:29 AM     Remind Me!  Send Private Message   Edit Post      
Screwed into the side of the drier is a low/high pressure switch(dual pressure). Its operation is as follows:

If the pressure is below 30spi the switch is OFF. The AC will not switch on. This is by design to protect the compressor.

If the pressure is above 340psi the switch is OFF. This is also by design. This is to protect from an over-pressure condition that could indicate a restriction, bad expansion valve. It's primarily a safety system. NOTE: The compressor has its own internal pressure based bypass switch as well.

The switch outputs an ON above 30psi and below 340psi.

This is why you must get a minumim amount of refrigerant into the system to get it to start.

The compressor can be turned by hand. With the engine off simple put your fingers inside the bell and spin the center (not the outside which is on a bearing until the clutch is activated). It should spin freely with only minor drag and no catching, no noises.

Remember a belt driven AC system is an entirely mechanical system. The electrical side of things is nothing more than interlocks, switch, fans and temperature based feedback for toggling the compressor clutch. All electrical control is in turning on/off the clutch and fans. Nothing more.



Stephen Firestone
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Galant VR-4 org Post #: 348624 posted 06/11/06 09:31 AM     Remind Me!  Send Private Message   Edit Post      
Thats very helpfull thank you. well i guess if i was looking for a break in the system it wouldnt hurt to check this switch to see if its on or off. if the switch is on, i should go grab a new belt? as long as the compressor spins freely.


Edited by DSMTurbo2 (06/11/06 09:32 AM)

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Galant VR-4 org Post #: 348627 posted 06/11/06 09:39 AM     Remind Me!  Send Private Message   Edit Post   
So if I want to convert to R134a, I should extract the R12, open up the system, replace the O-rings, drain the compressor, then put it back together with a new dryer?

Or is there another way to get the oil out? My A/C still works, I just feel like it should be able to get colder than it does.

Rob



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