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Discussion Starter · #1 ·
One of my cars (1993) came with R12 system. A/C hasn't worked since I've had it and I'd like to fix it. I'm replacing a/c dryer/accumulator, there's new condenser on it. Can I use a/c compressor with R134a or do I have to swap out a/c compressor too, they're very expensive.
 

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1: Check the orifice tube, replace with a blue one.
2: Dump about 3-4 ounces(measure it) of synthetic PAG in the hose for the reciever dryer. That replaces the oil that should be present all together in the two components you are replacing.
Synthetic PAG mixes with all oils, even mineral oil. Do not use synthetic ester, that is so yesteday.SY PAG is far superior.
use an ISO 100 viscosity synthetic PAG oil.

When you add the oil, try to hold the hode end high so you can be sure the oil runs into the drier. If it lays in the hose, when you charge the system it could hydro lock the compressor.:pain:
The charge amount you need to run with R 134a is 85% of the amount of R 12 it calls for.
 

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Discussion Starter · #4 ·
1: Check the orifice tube, replace with a blue one.
2: Dump about 3-4 ounces(measure it) of synthetic PAG in the hose for the reciever dryer. That replaces the oil that should be present all together in the two components you are replacing.
Synthetic PAG mixes with all oils, even mineral oil. Do not use synthetic ester, that is so yesteday.SY PAG is far superior.
use an ISO 100 viscosity synthetic PAG oil.

When you add the oil, try to hold the hode end high so you can be sure the oil runs into the drier. If it lays in the hose, when you charge the system it could hydro lock the compressor.:pain:
The charge amount you need to run with R 134a is 85% of the amount of R 12 it calls for.
Orifice tube? Do you mean schraeder valves?
 

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Many US manufacturers use an orifice tube. It functions in place of an expansion valve.
It is the calibrated restriction in the system that allows pressure to build on the one side, to form a differential in pressure.
In other words, it backs up pressure from the condenser/compressor, like a traffic jam, then becuase of the pressure and cooling of the freon at the condenser, liquid forms which squirts through the restriction into the evaporator core, where because of the low pressure it evaporates, extracting heat.
Usually they are in the line to the evaporator core,sometimes they are right in the inlet to the evaporator.
They can become blocked with small debris and cause damage to the sytem and compressor. Its allways a good idea to check them/replace them.When retrofitting to 134a its a normal procedure to change the tube to a different size. They are color coded for ease of identification of actual orifice size. Blue has a .067 inch size tube in it.
 

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Discussion Starter · #6 ·
1: Check the orifice tube, replace with a blue one.
2: Dump about 3-4 ounces(measure it) of synthetic PAG in the hose for the reciever dryer. That replaces the oil that should be present all together in the two components you are replacing.
Synthetic PAG mixes with all oils, even mineral oil. Do not use synthetic ester, that is so yesteday.SY PAG is far superior.
use an ISO 100 viscosity synthetic PAG oil.

When you add the oil, try to hold the hode end high so you can be sure the oil runs into the drier. If it lays in the hose, when you charge the system it could hydro lock the compressor.:pain:
The charge amount you need to run with R 134a is 85% of the amount of R 12 it calls for.
PAG 100 is medium viscosity oil, is that what I should use?
http://www.oreillyauto.com/site/c/d...924&categoryRedirect=N0491&pt=N0491&ppt=C0050
 

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That is not a synthetic and may not mix well with whatever traces of oil left over from when it had R 12 in it.
The 100 viscosity is thicker than GM uses typically, which is a ISO 46. BUT GM compressors dont seem to do so well with the lighter oil.
The ISO 100 viscosity helps compressor life and synthetic mixes with anything.
The brand is actually called "supercool" . Just google it.
Or if O reilly has an ISO 100 Syntheic PAG use that.
 

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Discussion Starter · #9 ·
I also have 01 Ram I'm trying to fix A/C (its hot here) AC is blowing warm air and I added a can of R134a last summer and it was blowing cold air for a while.
This year comes and it's blowing warm air just like before I've charged it.
So I've put a manifold on there...
When truck is not running
low pressure reads ~74 psi
high pressure reads ~75psi
When truck is running
low pressure goes up to ~47 psi and drops down (a/c switches)
high pressure goes up to ~100 psi and drops down a bit.
Is there a congestion in system somewhere or my system is overcharged/undercharged?
 

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Discussion Starter · #11 ·
I also have 01 Ram I'm trying to fix A/C (its hot here) AC is blowing warm air and I added a can of R134a last summer and it was blowing cold air for a while.
This year comes and it's blowing warm air just like before I've charged it.
So I've put a manifold on there...
When truck is not running
low pressure reads ~74 psi
high pressure reads ~75psi
When truck is running
low pressure goes up to ~47 psi and drops down (a/c switches)
high pressure goes up to ~100 psi and drops down a bit.
Is there a congestion in system somewhere or my system is overcharged/undercharged?
I've uploaded video of it here...
A/C cycling on and off, blows warm air - YouTube
Can anyone diagnose it for me?
 
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