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R-12 to R-134a Conversion

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Hi all, finally getting into wrenching again and have a couple questions for the Collective.

I'm in the middle of converting my R-12 A/C NSX to R-134a. I'm replacing the compressor with Denso 471-1194 (and swapping the pulley/coil assy from the old comp with old bearing unfortunately), new O-rings wherever possible, Denso L/H port conversion kit and labels, Denso ND-8 oil, and Freon brand Freon.

My old compressor was quite loud when the clutch was engaged, and I was running low on R-12 hence the conversion undertaking since no one works on R-12 anymore - frothy sight glass and barely cooling the driver's side vents due to insufficient liquid refrigerant to the evap. I've already swapped over the new compressor and hose O-rings and am currently running with the A/C clutch fuse pulled and no pulley belt until I can get the rest done. There was no "black death" or signs of contamination in the old comp or the lines that I've flushed so far.

1) When I opened up the old compressor, not a single drop of oil came out, so the FSM method of equalizing the mL of oil between the old & new compressors is useless. Since I'm flushing the entire system, how much oil total should I add? The new compressor came with ~110 mL already, and I filled about 100 mL of that back into the outlet side of the new compressor before installation (that's proper, right? Not into the inlet side so I don't hydrolock it?).

Google told me the total oil is ~147-162 mL (per https://www.techchoiceparts.com/refrigerant-and-oil-capacities/acura), is this true? The FSM table of oil capacities on pg. 22-65 is practically useless for me since it's unclear how many "20 mL" line or hoses I'm really flushing out and there was no oil to drain from the old comp.

2) I bought two green O-ring kits (Rapid Seal 26744 and 26745), plus the new compressor came with new black hose O-rings. Unfortunately the black Denso O-rings appear to be thicker than the old O-rings and they don't seem to be able to push fully into the fitting recess, so I used thinner green O-rings. Are they meant to be thicker and very hard to seat fully (can't really get it flush by hand), or will a thinner O-ring work fine? Not sure how thin is too thin.

3) What's the proper hose mounting bolt torque? Pg. 22-65 says 22 N*m and pg. 22-77 says 30 N*m.

4) What are the proper ranges for low/high side pressures that I should be looking for when charging? I read on Prime that it should be about 28 psi low/175 psi high +/- 10 psi @ 1500 RPM and there should be some bubbles in the sight glass at idle.

5) Maybe unrelated, but why did my A/C seem to randomly come on before this? My CCU is rebuilt and fully functional, but sometimes I'd be driving around with the A/C OFF and occasionally I'd feel the A/C kick on for a minute or two by itself. Not sure if that's normal functionality or not.

Thanks in advance.
 
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AC conversion

Just a few notes. Since your doing a complete and proper conversion best check with Kaz just to be sure for the l/s conversion. He by far knows all the important bits to make sure you don’t have any wasted time and money. I’ve always gone for around 35 on the low side and don’t go much over 180 or so on the high side. Higher could blow the seal, I’ve been told.
Kaz will know the closest to exact quantity of oil to install after a complete tear down and flush.
While your going to the extent your going to, replace all the o-rings in the system with new green ones. They say they are of a different make up that isn’t affected by R-134 Freon.
Just a few thoughts. Hope it helps a bit.

Cheers
nigel
 
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I did end up finding this post (http://www.nsxprime.com/forum/showt...vice-needed!?p=1944942&viewfull=1#post1944942) where Kaz says the new compressor is pre-filled with the total amount of oil for the system, in my case I drained about 110mL and refilled about 100mL. He also includes a good explanation of the charging amounts to expect. Gold (RIP) further down also says about 120-140mL total so I should be within that range by adding some dye and a bit of extra oil to get within that range, including the oil leftover from being unable to flush the evap in the car.

This thread is also useful for future reference on compressor selection (http://www.nsxprime.com/forum/showt...ith-a-94-or-newer/page2?p=1996629#post1996629).

I'll be trying to finish up the system tomorrow so I'll be updating my build thread with the results :rolleyes:
 
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I did the same years ago, I replaced the compressor and accumulator in front of the radiator. I replace o- rings only where I took the system apart with new green o-rings. All parts were purchased from Rock Auto. Before installing the compressor I drained all the existing oil. I then added the oil requirement and quantity mentioned in the service manual for a later model R-134a system.
I then evacuated the system using a HVAC vacuum system. I left it ran for three full weeks.
Then R-134a
NSX A/C 134a charge weight.
1.9 lb; 0.85 - 0.90kg
28.2 - 30oz
27-28 low side 179-175 high side


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Thanks. I flushed and buttoned up the system yesterday and was able to replace all the O-rings (besides in the evap) and pulled a vacuum for 1.5 hours to test and get the moisture away from my new oil & drier, but left it at that since I noticed my front condenser lines had a bad kink or two so I'm working on getting new ones to replace before I charge with R-134a. The line between the two condensers was kinked pretty badly so probably was getting a big pressure drop.

You pulled a vacuum for 3 weeks? That's dedication. I don't think my Harbor Freight vacuum pump would last that long :eek:
 
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Thanks. I flushed and buttoned up the system yesterday and was able to replace all the O-rings (besides in the evap) and pulled a vacuum for 1.5 hours to test and get the moisture away from my new oil & drier, but left it at that since I noticed my front condenser lines had a bad kink or two so I'm working on getting new ones to replace before I charge with R-134a. The line between the two condensers was kinked pretty badly so probably was getting a big pressure drop.

You pulled a vacuum for 3 weeks? That's dedication. I don't think my Harbor Freight vacuum pump would last that long :eek:

It was in the midsole of winter. My neighbour is a refrig mech and he lent me the commercial pump. We got to the new Freon when we could.


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