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Air conditioning; R12 vs R134 compatabilty
Topic Started: Jul 22 2009, 08:05 PM (1,922 Views)
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I know that there are those of you that would try to talk me out of installing ac in a convertible but my wife does not like the extreme heat[not that we've had much here this year] The prior owner removed the parts under the hood but I was able to pick up all the parts needed from an 89 metro for cheap when I started to think that I might be going about this the wrong way. As I understand it the 1994 metro used R134. Is that system a direct bolt on under the hood or should I just convert to R134. I had an unsuccessful attempt at converting one years ago with one of the diy kits sold in the automotive store. Thanks Rich
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Johnny Mullet
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Fear the Mullet

If you could find A/C parts from a R134 system, you would have less chances of leaks or problems. It should all bolt up the same.
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Thanks for the quick answer Johny I'm assuming you mean any R 134 not just the 134. I'm sure disappointed that I will not get a chance to meet you this year.
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Also if I went with the more current R134 system would that require replacing the evaporator or could I use the original and avoid having to work under the dash?
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Please just call me; "Schultz"

The older cars with R12 used different fittings than the newer ones with R134.
If you decide to use the R134 parts you will end up buying all of them. :smackface
But it is a direct bolt up. :thumb

Been there, (Thought I was bein' Mr. Super Smarty Pants).
Done that, (I weren't).

But I've done several conversions on these.
You can't sell one in Ole' Virginny without A/C.
They work quite well and last a decent long time.
Lemon Peasy.
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i have performed hundreds of r12 to r134a retrofits ,
but zero on a geo metro .

wear goggles

if you find black death anywhere , the component with black death gets pronounced , if the black death is throughout the system ...
this is not going to work , stop now .

there are service port adapters that screw on the the r12 fittings so that you can connect r134a equipment .
replace the schrader valves
replace the receiver dryer ,

dump all the oil in the compressor out , all the oil , if the oil is black and has anything but oil in it
the compressor is fraked .. the black stuff is black death , chunks of the inside of the hoses ...polished off by metal chunks from the fraked compressor as they went by.

wear goggles

if no black stuff , refill the compressor with the specified amount of the specified PAG oil from a post 1994 system
specified amount of same PAG oil into the NEW r134a compatible receiver dryer .

r12 oil is not soluble in R134a , you may not leave the r12 oil in the system , you will have a problem if you do .
a little bit of r12 oil can remain , it will collect at the bottom of the evaporator and just stay there ,
do not calculate that amount of oil into the amount of the correct specified PAG oil that you add to the system .
too much oil or too little oil is bad , use specified amount .use specified type of PAG oil ,

new green 0 rings every where a connection exists , lube the 0 ring s with white silicone grease or PAG oil prior to assembly to avoid pinching the rubber on the way in , use anti seize at all connections but do not get anti seize on the 0 rings .
do not torque the connections like you were king kong
snug and a little bit more is plenty , the 0 ring seals it , making it tighter just distorts the soft aluminum threads and adds misery to your life when you go to disassemble the connection in the future

remove the condenser and twist and turn and get all the oil in it out . again , no black death is allowed .
specified amount of PAG oil in the condenser .
make sure no air can spill around the condenser from the condenser fan , seal the edges with foam from the hardware store or aluminum flashing or whatever it takes .
this is very critical and an often overlooked cause of hi system pressure and poor cooling at idle in hot ambient conditions .

wear goggles

R12 and R134a expansion valve s are usually different .
imho , it is the only part that you may NEED to locate from a newer system ,
and R12 expansion valve will not give the low low side pressure that is needed for great cooling in a R134a retrofit, but an R12 expansion valve in an R134a system will provide some cooling usually.

you MUST apply vacuum ,
longer is better , it will take a few hours with a great vacuum pump to bring that system down after it has been open so long
my vacuum pump is 8CFM and will bring vacuum down to 40 microns , measured . atmosphere is 760,000 microns , outer space 0 microns
i would apply 4 hours of vacuum , leave it overnight with gauges connected and valves closed then 1 more hour or down under 100 microns BEFORE charging the system
. this is the most critical step .
a crap vacuum pump will work sorta kinda .

read this http://www.robinair.com/acsolutions/acvacuum/acvacuum.htm

then charge it WITH THE SPECIFIED amount of r134a from a newer post 1994 system , more is not better .
verify system pressure and verify that the condenser fan operates when pressure starts to get high , if the condenser fan does not run 2 minutes into the procedure STOP and find out why or you will damage the system and possibly injure yourself when a line blows off .
wear goggle s
Edited by mwebb, Jul 22 2009, 11:25 PM.
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Great details! I felt the desire to wear my goggles just to finish reading it.
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i intend to die , when i am 107 , with two very functional eyes .
so i wear goggles
around things that might change my goal
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