C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

A/C conversion

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Old Feb 25, 2019 | 04:32 PM
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Default A/C conversion

Hey guys and girls

I have an 88 C4 and I am going to convert the A/C from R12 to R134a I have the adapters and the R12 system is empty I have all the tools for R134a but do not know how much R134a I should use to get the correct level does any one know, also I will replace the drier and hoping there is nothing else I need to replace unless you guys/girls know different.

Any help will be gratefully received.


Gary alias Jagvette

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Old Feb 25, 2019 | 08:13 PM
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I believe the new dryer doesn’t have the low charge valve on it. You will have to replace the low pressure line with one with the valve. Don’t forget to add the refrigerant oil too. System holds around 3 small cans of 134

Last edited by Gunho; Feb 25, 2019 at 08:14 PM.
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Old Feb 25, 2019 | 09:55 PM
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A little yellow tracer would be good for future leak detection.

Are you also replacing the evap. valve?
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Old Feb 26, 2019 | 06:57 AM
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Standard rule of thumb is to use 75-80% of the R12 charge.
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Old Feb 28, 2019 | 06:22 PM
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good point
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Old Feb 28, 2019 | 06:23 PM
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that sounds like a good idea is this something that must be done, my knowledge of A/C is limited.
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Old Feb 28, 2019 | 06:24 PM
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OK, do you happen to know how much R12 the system originally had ?
,
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Old Feb 28, 2019 | 06:25 PM
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yes I will put oil in, but doesn't the r12 to r134 have the adapter valve ?
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Old Feb 28, 2019 | 06:35 PM
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Originally Posted by jagvette
yes I will put oil in, but doesn't the r12 to r134 have the adapter valve ?
Yes there are adaptor valves. But if you change the dryer, the new dryer won’t have one on it as they moved it to the hose on newer systems. Could be different on your year. But they did on my sons 93. As the valve was on the dryer.

Last edited by Gunho; Feb 28, 2019 at 06:36 PM.
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Old Feb 28, 2019 | 08:18 PM
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Originally Posted by jagvette
OK, do you happen to know how much R12 the system originally had ?
,
There should be a sticker under the hood listing the factory charge. IIRC my 89 is 44oz of refrigerant/ 8 oz of oil.
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Old Feb 28, 2019 | 11:15 PM
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Is there some sort of cleaner to run through an r12 system before converting to r134, or is it just a matter of the system being empty and that's good enough?
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Old Mar 1, 2019 | 08:48 AM
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Originally Posted by Maldini
Is there some sort of cleaner to run through an r12 system before converting to r134, or is it just a matter of the system being empty and that's good enough?
Yes, there is an A/C flush. You should use the "pop" method to try and clean out the evaporator.
Take off the compressor and drain it.
Take off the condenser and drain/flush it.
Replace all of the old hoses.

Also, change out all of your o-rings to the green RES style. And, if you did not know, mineral oil is not compatible with R134A. You need to use a PAG oil or a new type of ester (compatible with both).
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Old Mar 1, 2019 | 09:30 PM
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None of the OEM A/C unit manufacturers (non-automotive) recommend any of the flush products. The flush kits are designed to remove residual
mineral oil from the system but a few percent mineral in the system is less damaging than any residual flush left in the system from an inadequate
evacuation. Blow out all the residual oil with nitrogen (or air if you have to) and put in the proper oil. Evacuate and charge to 80% of R12 capacity.
Then enjoy the chill.
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Old Mar 3, 2019 | 12:48 PM
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I did mine on my 93.
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