R12 TO R134 Conversion

[VAL]

Well, a couple of years ago I had all the A/C components replaced with new parts(condenser, compressor, dryer, ect.) I haven't used my A/C for the last 9 months. Today I took it to the shop to get it charged up, and was told that R12 refrigerant is $55 a can, WTF! I'm looking for info on what's all involved in converting the system to r134. And will it work better, same or worse(temp and efficiency wise)? If I remember correctly when I had the current system installed, the components would work with both r12 or r134.

 

[Boone83K10]

You will need a flush, then r134 ports, New orifice tube, ether oil . R134 is not as efficient as r12 but it cools just fine. If you have work done for you, expect to pay big.

 

[chengny]

No component changes are required to switch over from R12 to 134a. All the currently installed parts can remain and will work just fine with a 134a charge. You might want to change to replace the filter drier and the expansion tube. The filter drier is that big silver canister attached to the evaporator housing. The expansion tube is accessible by opening the fitting that connects the liquid line to the evaporator inlet.

Filter drier:

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Expansion tube:

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Couple of notes:

You will have to dump the remaining R12 before anything else is done. You can release it to atmosphere, but certified shops cannot.

They have special re-re (refrigerant recovery) equipment that captures the R12. When they have a full bottle it gets sold to a facility that purifies and repackages it for re-sale. The production of new R-12 was banned worldwide years ago, so the only source is what can be reclaimed.

Anyway, if a shop does this conversion, that recovery process will trigger an extra charge. If you do it yourself it is free.

Whatever way you do it, after the system gets dumped, it will need to be flushed, evacuated and recharged with 134a.

Flushing is required because the oil used with R-12 is non-compatible with the oil used with 134a. There is a specific, involved, expensive way to do this - or there is the easy way. Provided your system is not being changed over due to a "black death" casualty you can do it with all the components in place and using just compressed air.

Black death is just a term used to describe a refrigeration system that has been disabled due to a catastrophic failure of the compressor. All the components and connecting tubing/hoses are contaminated with burnt (caked on) oil and all the metal particles that resulted from the compressor failure.

Release all the tubing fittings that connect the 3 main components (compressor, condenser & evaporator). Remove the suction/discharge hose manifold from the back of the condenser. Pull the existing expansion tube from the tubing that leads into the evap. Remove the filter drier.

Using 100 psi compressed air at a good volume:

Blow the residual oil from the condenser and evaporator coils. Do this in in both directions. Repeat until you feel that the bulk of the old oil is removed.

Blow out the liquid line that connects the condenser to the evaporator.

Blow out both compressor hoses.


Understand that the old R-12 oil is not like "poison" to the newly added 134a - it just does not circulate as well. So if there is a bit that remains in the system it will not be an issue.

That's it for flushing.

Using new o-rings at the fittings, replace your filter drier and expansion tubing.

Add PAG 100 oil in quantities as below and close the system up.

•Compressor- (1 ounce)
•Evaporator - (3 ounces)
•Condenser - (1 ounce)
•Accumulator (2 ounces)

Evacuate, leak check (system should hold 28" Hg overnight) and charge with about 50 ounces (4 cans) of 134a. You will have to jump your low pressure cut-out switch to get the first 2 cans in. After that the system will have enough pressure to allow the low pressure switch to operate normally and keep the compressor running.

You will need to buy a set of adapters for the service ports so you can charge and attach your gauges - if you have them. The adapters just screw on to the existing service ports.

 

[79azc10]

Holy cow your are a life saver . I'm being researching for a bit now and your post definiy saved me everything i had a question about u answered

 

[79azc10]

Val - don't know what side of town you live on but u could call this guy , thought about getting ahold of him. http://tucson.craigslist.org/pts/4407780849.html

 

[highdesertrange]

good advice so far. I would like to add 134 being not as efficient. the system will not blow as cold without allot of air flow over the condenser. in stop and go for long periods you will notice. an electric fan on the condenser will almost eliminate this. highdesertranger

 

[chengny]

For 79azc10:

Areas where I use silicone:

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Foam weather seal to seal the box to the fire wall:

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And don't forget to seal the heater core division plate (with the foam weather seal):

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[79azc10]

Thanks again , this helps a lot. I wish I could buy u a beer.

 

[VAL]

For 79azc10:

Areas where I use silicone:

You must be registered for see images attach

Foam weather seal to seal the box to the fire wall:

You must be registered for see images attach

All my a/c components have at some point been replaced except for the evaporator. Would it be beneficial to put a new one in?

And don't forget to seal the heater core division plate (with the foam weather seal):

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All my a/c components have at some point been replaced except for the evaporator. Would it be beneficial to put a new one in? And how do you jump the low pressure switch?

 

[chengny]

You need to " force feed " the initial charge into the system. This requires the low side switch to be closed.

Just pull the plug off the switch (located on the receiver/drier shell) and place a jumper across the two terminals of the wiring harness. This will cause the compressor clutch to engage. When the compressor pulls the low side down, you can then introduce a can or two of 134a into the system.

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After that, plug the harness back onto the switch - it will function as normal.

With the engine/compressor running, feel the low side pipe. As you near the proper charge, it should get cool and condensation will begin to form on the outer walls of the aluminum.

Don't overcharge the system. If - on the hottest day where you live - the air coming out of the dash vents is not cold (more than like 45 F) add just a little tiny bit more refrigerant.

 

[foamypirate]

Another good rule of thumb for charging is that the evaporator inlet and outlet should be approximately the same temperature. That way you are getting maximum cooling through the evaporator and aren't overcharged/undercharged. An overcharge runs the risk of slugging the compressor if the accumulator and evaporator can't return the liquid refrigerant back to a vapor state. An undercharge can kill the compressor by not providing enough lubrication to the compressor.

 

[VAL]

What about the oil that's in the compressor, is there a special way to flush it? Does it need to be removed?

 

[chengny]

There is hardly any oil capacity in the compressor - maybe an ounce max. To get what little oil might still be in there out:

Tilt the compressor so that the 2 inlet/outlet ports are at the low point and facing down. Shake the compressor to get the bulk of the oil out.

Then, while still holding the compressor in that position, use the outer face of the clutch plate to rotate the internals. Go a few revolutions in each direction. A few final drops of oil will come out of each port.

Do that until you feel you have pumped all the old oil out.


As above:

Understand that the old R-12 oil is not like "poison" to the newly added 134a/oil - it just does not circulate with the refrigerant as well. Flush as much out as you can, but don't stress if there is a bit that remains in the system. It will not be an issue.

 

[VAL]

There is hardly any oil capacity in the compressor - maybe an ounce max. To get what little oil might still be in there out:

Tilt the compressor so that the 2 inlet/outlet ports are at the low point and facing down. Shake the compressor to get the bulk of the oil out.

Then, while still holding the compressor in that position, use the outer face of the clutch plate to rotate the internals. Go a few revolutions in each direction. A few final drops of oil will come out of each port.

Do that until you feel you have pumped all the old oil out.


As above:

Understand that the old R-12 oil is not like "poison" to the newly added 134a/oil - it just does not circulate with the refrigerant as well. Flush as much out as you can, but don't stress if there is a bit that remains in the system. It will not be an issue.

This is the retrofit kit I bought, The cans of refrigerant already have oil in them. Do I still need to add oil to the compressor, condenser, and drier? Or will this work just how it is?

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[chengny]

I don't know for sure how much oil is in each 12 ounce can of EZ Chill 134a & Oil. I believe it is 2.5 ounces. That is important.

Your system requires 48 ounces of 134a (see below) and 6-7 ounces of oil.

So, lets say you dump all the contents (of the 3 cans that come with the kit) into your system.

As far as oil, you will have pretty much the correct amount (3 X 2.5 = 7.5 oz). A little extra oil will not effect cooling capacity or harm the components. That is based on my number of 2.5 oz per can - read the label yourself to check. If it is 3 oz per can - that is okay.

As for refrigerant, you will be short if you use only what comes in the kit. Buy an additional 12 ounce can of 134a. That can should be straight 134a - DO NOT get 134a with oil additive. You will be pushing your luck if any more oil is added - it may start to effect cooling capacity.

What happens is, an overcharge of oil can "pool up" in certain sections of the system. At some point - if they get big enough - these pools will begin to restrict the normal flow of refrigerant through the tubing and heat exchangers.


Here is how the refrigerant charge for 134a is determined:

When an R-12 system is retrofitted to 134a, the general rule of thumb is that the refrigerant capacity/charge should be reduced to 80-90 % of the original capacity.

The original GM spec for these trucks was 56 ounces of R-12. So, if we take 56 ounces of R-12 and multiply it by .85, we get a 134a charge of 48 ounces.

But, to answer your question:


Do I still need to add oil to the compressor, condenser, and drier? Or will this work just how it is?

No you don't need to add any more oil. And it doesn't really matter where you add oil to a system. Within a matter of minutes after starting it up, the oil mixes into the refrigerant and begins to flow along with it. There is no oil level in the compressor for example. As the compressor sucks in and pumps out the refrigerant, it's internals are lubricated by the oil entrained in the refrigerant. Basically, the oil is everywhere throughout the system and is constantly moving along with the 134a.