A/C Compressor replace with a 94 or newer?

[bonhamsurf]

The refrigerant is pretty much a non-issue. Yes, the seals are different because the R-134a molecule is much smaller, but existing oil impregnated o-rings seem to have no problem. AFAIK there is no upgraded vanes to compensate for the higher pressures that R-134a puts out. So for all intents and purposes the R12 parts work just fine with R-134a.

Just make sure your shop is buying a quality JP re/made part. An Even Bigger Project will be to clear Black Death from your A/C system in the event of an internal failure; do you do not want this at all.

I recommend you keep your OEM compressor and clutch just in case there is an issue. At least have them extract the pulley and hookups if space is an issue. The compressor is quite simple to rebuild yourself depending on the type of failure.

I rarely overrule boots on the ground. My only issue is that generally used OEM is often superior to new aftermarket.

So you'd go with the 1991 OEM Fitment/R12 Denso 471-1421 and have the AC repair guy just do an oil change to make it work with the R134? He suggests this so that I get a new clutch and not re-use my old clutch

Or go with the 1994+ Denso 471-1994 that is already R134 rated, and re-use my existing pulley?

 

[drew]

So only the 1991 comes with a new clutch? And the 1994 doesn't? The clutches should be the same spec...is there a price difference?

There should be green seals on the 1994+, and not the black ones.

Also replacing ONLY the clutch in vehicle is not a huge job.

 

[bonhamsurf]

So only the 1991 comes with a new clutch? And the 1994 doesn't? The clutches should be the same spec...is there a price difference?

There should be green seals on the 1994+, and not the black ones.

Also replacing ONLY the clutch in vehicle is not a huge job.

Apparently the pulley is smaller for the 1991 than the 1994. So I'd have to reuse my old pulley (does that also mean reuse the entire clutch??)
If I buy the newer compressor.
Or just get 1991 R12 spec compressor and pulley and change oil to use r134?

Sent from my SM-G973U using Tapatalk

 

[drew]

>Apparently the pulley is smaller for the 1991 than the 1994.

I'm having a hard time with this one. I don't know, but I don't think the size difference would be appreciable.

The belt p/n: 38920-PR7-A01 is 38920-PR7-A02, which both translate into 4PK975 (4 rib, 975mm length)

I'm calling the shop out: those two pulleys are effectively the same. In fact, Gates is stating their K040384 belt fits all years NSX.

 

[bonhamsurf]

>Apparently the pulley is smaller for the 1991 than the 1994.

I'm having a hard time with this one. I don't know, but I don't think the size difference would be appreciable.

The belt p/n: 38920-PR7-A01 is 38920-PR7-A02, which both translate into 4PK975 (4 rib, 975mm length)

I'm calling the shop out: those two pulleys are effectively the same. In fact, Gates is stating their K040384 belt fits all years NSX.

The shop didn't say the pulley was smaller, other posts on Prime mentioned this. If the pulley and the clutch on the 91 Denso is the same as the 94+ Denso, then it makes sense for me to just order the 94+ that's already R134 compliant.
My AC repair guy only said he doesn't suggest ordering one that would require changing the pulley and/or clutch as he doesn't think it makes sense to reuse my old clutch

Sent from my SM-G973U using Tapatalk

 

[bonhamsurf]

>Apparently the pulley is smaller for the 1991 than the 1994.

I'm having a hard time with this one. I don't know, but I don't think the size difference would be appreciable.

The belt p/n: 38920-PR7-A01 is 38920-PR7-A02, which both translate into 4PK975 (4 rib, 975mm length)

I'm calling the shop out: those two pulleys are effectively the same. In fact, Gates is stating their K040384 belt fits all years NSX.

Wait a minute. I think I just realized, You're saying the pulley on the Denso 471-1424 (1991-1993 Size) and the Denso 471-1194 (1994+) are the same. Same pulley, same clutch, just the Freon compatibility (R12 vs R134) is the only difference between these 2 Compressors?

I ask because on Denso's website, the 471-1424 has a Clutch Maximum Diameter of 140mm https://www.densoproducts.com/product.aspx?zpid=10339
And the 471-1194 has a Clutch Maximum Diameter of 125MM https://www.densoproducts.com/product.aspx?zpid=10325

 

[drew]

The only effective difference between them is likely the color of the seals.

And a seal kit has to be only a few dollars.... and that really doesn't matter that much.

 

[bonhamsurf]

The only effective difference between them is likely the color of the seals.

And a seal kit has to be only a few dollars.... and that really doesn't matter that much.

Then it only makes sense to go with the 1994+ one as it's already R134. I wonder what that "Maximum Clutch Diameter" difference is. But if you say they're identical, I'll go with it.

 

[drew]

no effective difference <> identical

So upon quick research: the diameter of the crank pulley is the same for all NSX's, the a/c belt idler pulley is also the same and the a/c drive belt is the same for all NSXs.

Conclusion: no effective difference in a/c compressor pulley size

(all = minor exceptions, Type R's, etc...)

more research: it appears the clutch pulley is only applicable to the NSX for the Honda line up. It is possible that your a/c shops supplier is substituting a similar spec one instead of the OEM spec one.

 

[Kaz-kzukNA1]

	Refrigerant	Pulley Dia.	Pulley Offset	Connector
471-1194	R134a	125mm, too small	91-96 spec	wrong
471-1193	R134a	140mm	97+ spec	same as OEM
471-1424	R12	140mm	91-96 spec	same as OEM

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You seemed to have posted the similar subjects in several places so hope this one is the main one.

Above spread sheet shows the difference of the Denso re-man compressor.

Please note that I never dealt with 1424 and the info is from Denso Autoparts website.

For 1193, the info is based on my real experience. In fact, I have one at my place at the moment.
For 1194, the info is based on my experience while supporting another owner installing it.


If ordering the OEM compressor, it DOES NOT include the CL set (pressure plate/pulley/field coil).
You need to order them separately or re-use your existing ones.
On the other hand, above Denso aftermarket one comes with the complete new CL set.

Many people uses the word 'CL, Clutch' as an assy of clutch pressure plate/pulley/field coil.
For the clarification, I treat them as three different parts as per photo and refer them as pressure plate, pulley and field coil in this post.

OEM P9K compressor.

Denso 471-1193.

Extra info here; http://www.nsxcb.co.uk/entry.php?2321-Denso-Compressor-471-1193-4Seasons-Drier-33412-part-1

Bracket difference.
The fixing bolt hole position on the Eng block is the same so both are interchangeable.
The bolt hole on the compressor body is the same for 10PA15C body.
97+ bracket shifts the entire compressor towards outwards, just a few mm.
In order to keep the same alignment against the a/c belt idle pulley and crank shaft pulley, the compressor pulley offset was changed for 97+.




Your system is already converted to R134a but there are so many options/approaches/combinations that you can take so I'll just cover the basic.
Please select or combine these options.


The most important thing is to keep the combination of the pulley offset and the bracket as a pair.



471-1194:
Must deal with the connector unless re-using your existing field coil.
Many just cuts off the one from the existing one.

Must deal with the pulley diameter.
Swap in your existing pressure plate/pulley/field coil as a set.

Or, swap in your existing pulley but use the new pressure plate and the field coil came with the new compressor.
Requires dealing with the connector.
Never tried by myself but based on another owner's experience.

Or, just replace the pressure plate and re-use existing pulley and field coil.
Never tried by myself.



471-1193:
Must deal with the pulley offset.
Replace the mounting bracket on the eng block to the 97+ spec.
If using aftermarket header, you may need removing the front header first before removing the bracket.

Or, swap in your existing pressure/plate/pulley/field coil as a set.
Basically, just using the new compressor body and re-using the rest.
You can keep or sell the new pressure plate/pulley/field coil that came with the new compressor.



471-1424:
Must drain as much mineral oil as possible from the new compressor.
Kind of waste and any left-over stays inside the system as another debris.
It won't travel through the system and just stays at the lower section.



I normally recommend the owners to go for the 471-1193 and either just swap in the existing pressure plate/pulley/field coil from the old compressor or install the 97+ mounting bracket and use the whole new compressor as it is.



These are just some options you can take and there are many other options including combining some of the above points.

You can also consider just buying new or used pressure plate/pulley/field coil to suit your demand.


Kaz

 

[drew]

Kaz

Verify: the 140mm pulley won't clear with a 91-96 bracket?

Is the bearing replaceable on the clutch? appears to be a simple press in/out...

Is Ester oil recommended?

 

[bonhamsurf]

.....


These are just some options you can take and there are many other options including combining some of the above points.

You can also consider just buying new or used pressure plate/pulley/field coil to suit your demand.


Kaz

Thank you for all of this invaluable and amazing info. Is it safe to assume that all of your comparisons and potential need to change parts out is based on putting the new compressor into a 1991 NSX?
Thanks

 

[Kaz-kzukNA1]

Yes, but only with the R134a OEM new or overhauled compressor (body only, OEM doesn't come with the CL set) as part of retro-fit.
This means that the CL set (pressure plate/pulley/field coil) was either re-used from the existing one or OEM used set came as part of the overhauled compressor.

Based on what you wrote here and possibly on FB group, apology in advance if you already knew this but may I recommend considering the compressor and the CL set separately?

For example, OEM P9K compressor is used on many Honda/Acura models and it's also used on different make/models.
It's just the CL set difference.

From outside, regardless of R12 or R134a, the mounting hole geometry is the same between P9K and all three aftermarket ones in my above spreadsheet.
It's just the same 10PA15C type.


Same story goes for the CL set.
You can find the same CL set of NSX on different make/models.
That's what the owner did when he bought the 1194 by mistake.

His NSX is 97+ model so requires the CL set with 97+ offset but 1194 comes with 91-96 offset.
He got the 97+ one by buying the used compressor + CL set from one of the Toyota model.


I can see the point on what the A/C specialist mentioned about the very old and worn CL set.
I was on the same boat when I carried out the A/C refresh on my NSX.

At that time, I used OEM P9K compressor and wanted to replace the CL set to 97+ spec together with the 97+ bracket.
Unfortunately, due to back ordered parts, aftermarket header and available free time, I had no option but to re-use my 22 years old - 152K miles CL set.
That's the photo in the above post.


There must be a reason for replacing the compressor and it involves so many other tasks/parts/factors.

You just need to discuss with your A/C specialist and figure out the best option and balance the cost.
Depending on how far you want to go, A/C service could result in mega-expensive project.

I was fortunate enough to only top up the refrigerant once over 22 years (surprisingly) but I think it triggered the puncture of the evaporator forcing me to take the dashboard out for the A/C Refresh.

Good luck with the A/C service.

Kaz

Verify: the 140mm pulley won't clear with a 91-96 bracket?

Is the bearing replaceable on the clutch? appears to be a simple press in/out...

Is Ester oil recommended?

Hi, drew.

You want to stay with the 140mm pulley.
AT model has larger diameter crank pulley (not the a/c compressor one) so the ACG and the A/C compressor would be always spinning at higher speed at any Eng rpm than MT model.
Thus, there is some safety margin on the compressor side but not sure of the durability if 125mm was used.

Probably you are not familiar with the subject of offset at the mounting bracket and the pulley?

Hope these photos show you the difference.

The blue line is where the A/C idler pulley bracket sits so this geometry is the same between the two brackets.

The fixing hole geometry to the Eng block is also the same.

As you can see, the 97+ bracket will shift the entire [compressor + CL set] outwards, towards the Rear Right tyre for about 8mm.

At the same time, to install the A/C belt, you need to keep the alignment of the crank pulley/idler pulley/AC pulley in line.

Therefore, with 97+ bracket, you need to shift the AC pulley the other way round.
It will sit much closer to the compressor body to compensate the increased offset compared to the 91-96 version.

So, you must keep the combination of the bracket and the pulley as a set, just like above photo.

91-96 bracket for 91-96 pulley (sits away from compressor body) and the same goes for the 97+ of which the pulley sits really close to the compressor body.



Good point about the bearing.
I think it's possible but never done.
In fact, unlike the bearing at the A/C idler pulley, never felt any rattle.




Regarding the POE....
While I understand the benefit of POE, for Denso compressor that came with ND-OIL8, I would stay with the OIL8.
That's what I was recommended by my trusted compressor overhaul place in Japan.

With modern hybrid car with electrical compressor in use, it would specify the POE use for safety and design requirement.
It also benefits from no shaft being exposed to the atmosphere.

On the other hand, the classic compressor has high speed shaft spinning with the seal around it, just like the Eng WP.
Inevitably, the oil can seep over the years and also it could get in contact with the atmosphere/moisture.
ND-OIL8 has advantage in this area among other ordinary PAG oil.

The latest POE seemed to be very good and reliable ones are quite expensive.
Some aftermarket product companies are selling POE based so called 'A/C treatment, additive', just like lots of Eng oil additive on the market.

When POE was first introduced, I saw lots of trouble and since I don't have enough experience with it, I just follow what my trusted person told me.


Kaz

 

[bogle]

471-1193:
...
If using aftermarket header, you may need removing the front header first before removing the bracket.

Curious if anyone knows this for sure. Is it impossible or hard to swap in the 97+ bracket with aftermarket headers? Say comptech? The 1193 part seems like the ideal route, but I’d rather not need to unbolt the header...

 

[TANTO]

Curious if anyone knows this for sure. Is it impossible or hard to swap in the 97+ bracket with aftermarket headers? Say comptech? The 1193 part seems like the ideal route, but I’d rather not need to unbolt the header...

Since i have the comptech headers, i have ordered the late model bracket and pulley assy which i understand will get the compressor a whole 8mm (he-he) farther away from the header. I have long ago stocked in a bunch of R-12 and plan to stay with it. I purchased a rebuild kit for my OE compressor but found a little too much corrosion, so i now plan to order a new denso10PA15c/equiv which will likely have been assembled with 134 oil. I'm not thrilled about simply attempting to drain the 134 pre-charge and then guessing about the new R-12 mineral oil charge. To be totally safe, should i dissemble and re-lube?. Just want to take all precautions as i don't yet have a recovery set up. Any thoughts appreciated.

 

[bogle]

I did end up using the early r12 replacement compressor and I did remove the header (it is comptech). Removing the header wasn’t so bad and gave me a ton of rooom. I can tell you a bit about what I learned

There are 3 different oils you can use. Mineral oil, ester, and PAG. Mineral was in r12 systems, as you know, PAG is in factory r134 systems (and probably your compressor).

Mineral oil and PAG are not compatible, together they can cause “Black Death”. I don’t know how much of both would cause that, though.

The third oil is ester oil. It exists pretty much only as a conversion oil because it is compatible with both mineral and PAG. Usually a r12 to 134 conversion uses ester because you can’t get all the mineral oil out of the system.

No matter what oil you want to go with you will likely need to drain the compressor of its loaded oil, just to measure how much is in there. Even after draining it, there will be a ton of residue left in the compressor. I guess you could use solvent to get it out, but that seems like a lot of effort, and you may not even get it all out.

You can look to see on your denso compressor which one is has loaded. It’ll say ND oil 8 or something. IIRC 6 and 7 are mineral oils, and 8+ are PAG oils. I’d double check though.

After learning all this, if it were me I would go one of 2 ways

1. if I were replacing the compressor on an r12 car where the evaporator was not going to be replaced (it’s hard to flush), I would only use the early replacement compressor that is loaded with mineral oil. I’d do this because it seems like you can’t get the later compressor with mineral oil, the evap will have residual mineral oil, and I wouldn’t want to risk having any residual PAG oil in the compressor mixing with the mineral oil.

2. if I were replacing the compressor when the evap was being replaced or was known to be well flushed, I’d use the later compressor and PAG oil with 134. All the lines and condensers are easy to flush, and you’d replace the drier in all cases

I ended up going option one and converting to 134 with ester. The ac works great now the few times a year I use it.

 

[TANTO]

My compressor was original R-12. Couldn't find a new denso japan, so had to settle for a new denso china ($250-ebay) 471-1424 which i believe is the same 10PA15C my 92 came with. Denso's site "says" they all come with the original charge. Thanks for oil tag definers which will make me feel better about not flushing and re-oiling the new compressor. Sure hate to break it open for nothing. Only other gamble is my new evap which could have some PAG oil in it which i did not flush because it looked dry. I now wish i had flushed it also, but that unit is back in. Thanks bogle!

 

[drew]

Kudos dood! The first time around is painful because of all the new learning involved. Next time will be a lot easier and you'll find that clearing out lines isn't that difficult, just need the proper solvent, injector, and a compressor. AliExpress has what you need.

I went from paying a few grand for A/C work one day, to getting my MVAC license, and now this stuff is easy enough. My home became a service center for GFs, friends, and neighbors on A/C (among other things). I went to visit my uncle in Hawaii a couple of months ago and ended up doing his X5 A/C too.

Pro tip: Do NOT service your A/C in your front driveway where anybody can see it, or everybody will want it, and you'll watch your free time evaporate. You won't be able to step foot outside without somebody tracking you down...

Being useful is a curse.

 

[Kaz-kzukNA1]

My compressor was original R-12. Couldn't find a new denso japan, so had to settle for a new denso china ($250-ebay) 471-1424 which i believe is the same 10PA15C my 92 came with. Denso's site "says" they all come with the original charge. Thanks for oil tag definers which will make me feel better about not flushing and re-oiling the new compressor. Sure hate to break it open for nothing. Only other gamble is my new evap which could have some PAG oil in it which i did not flush because it looked dry. I now wish i had flushed it also, but that unit is back in. Thanks bogle!

Hope you checked the TSB and the amount on the oil tag.
If went with 471-1424, it may only had 80cc as that was the original OEM spec.
Later, Honda released TSB and increased it to 120 +/- 10cc.

 

[TANTO]

Thanks Kaz for mentioning SB-91-016, lots of interesting AC stuff there due to the r-12 to 134 conversions (if you read it he-he). Looks like they added 1.5 oz oil to all R-12 cars. Regarding the available Denso 471-1424 unit which seems to be the pick for R-12 cars. I assumed this $250 unit would be of China origin, yet the nameplate says made in Japan (see pic) A couple of things that didn't thrill. When i went to change to the late model clutch/pulley assy, while the snap ring groove is the same, the new denso snap ring was larger and looser. A sub par snap ring from a japanese Denso?-yes. Likely would be fine but it was too loose for me. I had a new snap ring from a non oe honda rebuild kit and it was a bit too small to get on! So i used by old OE o-ring (gasp now) because it still fit very well. There were also "gouge rings" around two of the compressor bolt holes looking like it was a rebuilt unit. Upon close up inspection they were from less-than-perfect tooling and not from old bolts. Denso appears to not be what it used to be( no Honda QC folks on their ass), but the price was right and time will tell about the insides. Now to my current concern - system/comp oil requirements. I don't see a "tag" on the as delivered oil amount. Since their paperwork says to check the level so trying to find out what it came with is mute. So i'm going to drain it and refill it. I'm seeing with all new dry components should be 5 oz oil , so i'm thinking 4.7 oz since the compressor will not totally drain. Being new to this ac stuff, can i simply just rely on this total oil charge IN the compressor for the whole system without putting any oil when charging? 32 oz to 34 oz by weight scale is my plan. Just received a new compressor hose connection plate from japan as it was a bit corroded around the bit o-ring (JPK for king!). Thanks for the follow, i'm on track to save a couple of months of the driving season.