Different Compressor Positions

One option was to trade in the R12 compressor that originally came with the vehicle and buy a rebuilt one, but at the time the price difference between a rebuilt and a new one was small, so I bought a new compressor for R134a. R134a was adopted as the refrigerant from the 1992 model year, but in models from 1997 onwards (NA2 and NA1 from the 140 series onwards), the compressor body is offset to the outside of the vehicle.
The mounting dimensions of the compressor body are the same for all model years, but in addition to the bracket being changed in models from 1997 onwards, which offsets the compressor to the outside, the pulley position of the clutch set is offset inwards so that the belt position is the same.
In other words, if you use either the bracket or the clutch set for models from 1997 onwards on their own, the pulley position will be misaligned, so you need to use both at the same time.
This change in the compressor's position coincides with the introduction of the C32B and the adoption of a fabricated exhaust manifold, so I suspect the compressor's position was changed to increase the clearance between the exhaust manifold and the compressor.

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Purchased compressor, bracket, and bolts

1. I purchased the compressor, bracket, and mounting bolts.
   Initially, I mistakenly thought the compressor was offset outwards because there was a difference in the mounting dimensions of the compressor body, so even though I planned to use the original clutch set, I ended up buying the bracket for the 1997 and later models as well.
   

Replace all O-rings for R134a

1. The piping has also deteriorated over time, and ideally I would like to replace it all with new parts, but considering the cost, I decided to replace only the O-rings. The compressor oil composition differs between R12 and R134a systems, so the material of the sealing material (O-ring) used is also different. Using R12 O-rings in an R134a refrigerant and oil environment can lead to material deterioration such as swelling and cracking, potentially resulting in refrigerant leaks.
   In general retrofit work, existing O-rings are often reused, so it is unlikely that problems will occur immediately. However, since I was planning to clean the inside of the piping, I decided to replace all the O-rings at the same time. In addition, the internal structure and materials of the high-pressure and low-pressure hoses connected to the compressor also differ between R12 and R134a. R134a hoses are thought to have a barrier structure using nylon-based material in the inner layer to prevent refrigerant permeation, so ideally they should be replaced, but considering the cost, I decided to reuse the hoses this time.

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Purchased O-rings (all for R134a)

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Receiver COMP. 80351-SL0-305

1. The receiver tank is a component that removes moisture and foreign matter from the refrigerant circuit, so it is always replaced during retrofit work. The brass plug attached to the receiver tank is a safety device called a "fusible plug." If the pressure in the air conditioning cycle rises abnormally due to a pressure switch malfunction or other reasons, the low-melting-point solder in the center melts, releasing the refrigerant and preventing circuit damage.
   This solder uses a material with a lower melting point than normal solder, and it seems to melt at around 70°C.
2. I purchased a retrofit kit.
   I ordered one for the NSX, but for some reason the high-pressure adapter plug didn't fit the plug on the R12 pipe, so I couldn't use it.
3. It turned out that the R134a tripressure switch (80440-SL0-901) I purchased was incompatible with the thread size of the R12 pipe, and therefore could not be used as is.

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Purchased retrofit kit

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R134a pressure switch has small threads

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Additional pipes purchased

1. The high-pressure side conversion plug and pressure switch have different screw sizes, so they cannot be used together as is.
   While it is possible to use a conversion adapter, selecting parts and checking compatibility was troublesome, so I decided to purchase an additional "pipe, receiver" for R134a that includes a high-pressure side service plug and pressure switch mounting section.
   In addition, "pipe A, condenser" and "pipe C, condenser," which are exposed near the front opening, showed damage from flying stones, so I also purchased replacement parts for them.