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Conversion back to R12

AR75TS on Sat January 24, 2009 5:16 AM User is offline

Year: 1988
Make: Ferrari
Model: 328
Engine Size: 3200
Refrigerant Type: R143a
Ambient Temp: 25C
Pressure Low: n/a
Pressure High: n/a
Country of Origin: New Zealand

No it's not mine!

Friend's 328 was converted to R134A a few years back. The AC in these was poor when new, with R134a it is laughable. Hard to tell it is actually going. Seems that 134 in these cars just doesn't cut the mustard.

Haven't put gauges on it as I had no 134 connectors. Sight glass shows just a few bubbles at 1500 rpm. Service label says 800g of 134, a full R12 charge is 1000g. Can't recall oil type used but will recheck (was on label).

So we are thinking of converting back to R12 (I have 15lb or so still). Obviously will replace dryer with new and remove the SD507 compressor and refill with new oil.

If the oil was mineral oil compatible (more than likely) would it be acceptable to flush what I can (probably remove condenser and evap) and refill with R12?


HECAT on Sat January 24, 2009 6:39 AM User is offline

It sounds like returning to R-12 is the right thing to do. Many sports cars have marginal A/C cooling from the start. IMHO, it has more to do with heat removal (condenser size limitations, air flow, and underhood temps), as it is not like they have a van size cabin to cool. At the age of this vehicle, the condenser may be tube and fin or serpentine design which is not the most efficient available today to produce good results using R-134. Oil flush the compressor (see procedure page for tips), use an evaporative & compatible solvent and blast the heat exchangers and then blow, blow, blow (nitrogen or "paint booth quality" filtered dry air); until you are sure everything is dry with no solvent residues remaining. With a fresh filter and the correct amount of fresh oil installed, you will be ready to vacuum and recharge with R-12. Good Luck, and enjoy the test drive(s).


HECAT: You support the Forum when you consider for your a/c parts.


mk378 on Sun January 25, 2009 6:41 PM User is offline

If PAG oil has been installed you will need to remove all of it very carefully. R-12 will react with any residual PAG and turn it into sludge.

Even if ester oil has been used it would still be very good to flush everything and install the proper amount of oil. Too much oil will cause poor performance even with the designed refrigerant.

Edited: Sun January 25, 2009 at 6:43 PM by mk378

TRB on Sun January 25, 2009 8:37 PM User is offlineView users profile

Might be best to go with a quality POE instead of mineral oil in this case.


When considering your next auto A/C purchase, please consider the site that supports you:

AR75TS on Fri February 20, 2009 4:31 AM User is offline

Finally identified the oil as ND8 PAG oil.

I will remove the pump and cleanse it with new mineral oil. Will change all the o-rings and flush the lines and components. New drier, check the expansion valve is appropriate and flush the evap and condensor well. I work at an airline engineering base so have ready access to decent flushing facilities.

Thankfully there is pretty good access to everything as it is all under the front hood. Just two lines running back to the Sanden pump sitting on top of the engine.

Edited: Fri February 20, 2009 at 4:40 AM by AR75TS

TRB on Fri February 20, 2009 10:20 AM User is offlineView users profile

ND8 is PAG46, when going back to R12 I would flush the system, drain the compressor and use either the BVA Auto 100 or a mineral oil. Drier change is a must when swapping oils and refrigerant. I also would try and dilute the PAG46 in the compressor but using some extra oil of choice turning the compressor and draining it. Then refill for the project at hand.


When considering your next auto A/C purchase, please consider the site that supports you:

Edited: Fri February 20, 2009 at 10:22 AM by TRB

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