AC advice requested

[VancouverBCnsx]

Out of the blue, my AC compressor started making a significant racket which I originally thought was an engine problem but thankfully was not. Up until that point, I believe the AC was functioning normally with R-12. Not absolutely sure as I seldom use the AC here in Vancouver Canada. The AC compressor is apparently not seized and moving freely. I have been driving without any noise by depressing the AC button and turning the AC off. The AC compressor has run for a very short period with the noise so I wonder if the risk of metal shards in the system is minimized.
I have a number of queries as to what options might be available.
1. Does no action at this point have any negative repercussions in terms of fixing the issue in future?
2. Is there a case to be made for simply removing the compressor and associated drive belt after evacuating the R-12 (and effectively lighten the vehicle)?
3. If I opt to replace the compressor and convert to R134-A, what exactly does the retrofit kit include? Does it include a receiver/dryer part?
4. Is there a way of capping the closed system when the AC compressor is replaced (ie avoid the evacuation of the system)?
Thanks

Marc

 

[SWFL_NSX]

I just replaced my compressor after it started moaning (see this thread). Before doing anything, I would check the bearing in the AC idler pully-it can fail and create a racket, mimicking the symptoms of a failing compressor (even sounding differently based on AC clutch engagement). Assuming that it is the compressor that is making noise:

1. I don't think there are any negative assuming a.) you keep the compressor off and b.) the system is not leaking. If you keep running the compressor it will throw more and more metal shavings into the system, which makes the eventual repair more difficult. If the system is leaking eventually you'll lose pressure completely and let moisture into the system, leading to corrosion and again making the eventual repair more difficult.

2. It's your vehicle and you can do what you wish with it, but it would decrease the value to a potential buyer and doesn't have much benefit for a non-race vehicle. I don't often go 120MPH, but I keep my car in a level of repair that would allow me to do so. I think the AC is similar.

3. I dont know what is included in the kit, but I don't think there is a receiver/drier. I would highly recommend checking out this thread from [MENTION=7722]Kaz[/MENTION] on his AC refresh: http://www.nsxcb.co.uk/entry.php?1836-AC-Refresh-01&bt=2601

4. There is no way to "cap" the system and keep the r-12 inside while the compressor is removed. You'll have to find a shop to evacuate the R-12 regardless of changing the compressor, switching to r-134, etc.

Hope this helps!
SWFL_NSX

 

[crxguy52]

I've done some AC work on other cars before, and the NSX system isn't too much different than them.

1. You can unplug the compressor (should be a small connector coming off the compressor) to make sure it doesn't kick on again, that would prevent you from accidentally turning it on. Shouldn't have any consequences.

2. I pulled the AC out of my CRX (and replaced basically the whole system in my Integra), and I can tell you that the compressor and bracket are >75% of the system weight. To completely remove the system you'd have to pull the dash out to remove the evaporator, plus the bumper to remove the condensers ( fuzzy on that second part, [MENTION=7722]Kaz[/MENTION] would know that). On top of that, it saved like 10, maybe 15 lb.

3. The Honda retrofit kit (TSB from the wiki) only includes the oil and fittings. It assumes the system isn't opened in the process, and therefore doesn't include changing the dryer. If you open the system, it's always a good idea to replace the dryer (also they're not expensive).

4. No way to cap it off, unfortunately. If you want to stay r12 I know [MENTION=16509]angus[/MENTION] may be able to hook you up

 

[VancouverBCnsx]

Thanks a lot for the info....much appreciated.

A thread from years past included a recommendation by Larry B. to use ester oil as the best option to flush the system. Do you know if that is the oil included in the retrofit kit?
I was planning to purchase the Denso 471-1424 which indicates in the literature that the OE specified o-rings and seals are compatible with both R12 and R134A. Is there a better choice?
Thanks again for the helpful comments

Marc

 

[Kaz-kzukNA1]

Hi, Marc. Got your message so here is my thoughts;

First, please check that the noise is definitely coming from the compressor and not something else.
Quite often, I had to replace the bearing at the a/c idle pulley for other owners as it started making squeaking noise. If the pulley itself is not damaged, you can just replace the bearing and re-use the pulley. Bearing itself is very cheap.


Please try using the a/c regularly even for a short period.
Best using it even in the cold weather.
If not, you will shorten the life of the a/c system.


1. Depends on the cause of the failure and whether you have any leakages or not.
If your CL fails, you will have huge friction while the engine is running even if you have disabled the compressor.
Best to remove the a/c belt.

Please note that if you leave the repair later, something that can be achieved now may not be the case later.
For example, the fitting that is just about possible to release now may get further corrosion and impossible to do so later.

Most of the time, delaying any a/c services will result in more parts replacement and thus, more labour charge.


2. Unless your NSX is mainly used for track day, personally, I won't remove the a/c.
As it says, it's air 'conditioner' and not 'cooler' so you use it throughout the year to control the humidity and temperature of the cabin air.
Useful in defogging the windshield in wet cold weather.
You don't want keep opening the window slightly in wet weather while cruising at the freeway/motorway speed.


3. Depends on the 'retrofit' kit you use.
I prefer using the Denso charge port adaptor that will force you removing the old Schrader valve before the installation.
The kit may include o-ring, PAG/POE oil, etc.

No point in keep using the old receiver/drier and hoping that it will be fine after the service.

The drier may have already nearly saturated or the bag could be already damaged due to vibration.
The filter may be partially blocked.

Doesn't need to be OEM and since it's such a cheap parts, just replace it.

Please check the diameter of the replacement one.
R12 one has larger capacity/diameter so your existing holder bracket won't fit if you switch to R134a one.
No a big problem as you can always use different method to hold it.
It doesn't need huge force as there are two pipes at the top. Just need something to prevent it from vibrating/moving.
Metal tyrap or something similar is good.


4. If disconnecting any of the fitting including the compressor, you must first recover the R12 refrigerant.
There is a tool to replace the Schrader valve without disturbing the closed system but no way for what you are planning to do.


5. This is for your latest post above;
If flushing the system because you are replacing the compressor, then personally, I would use flushing fluid such as the one from Four Seasons instead of POE.
Your new compressor is pre-filled with the specific type and amount of oil suitable for the system design of the NSX and the selection of refrigerant so no point in leaving POE in the system.

Or, take your NSX to the a/c specialist who has the expensive a/c service station that can flush the system by disconnecting the existing compressor.
It can measure not only the recovered amount of refrigerant but also the old compressor oil left in the system (manually measure the amount of oil stayed in the removed compressor).


By the way, you are probably aware of this but Denso 471-1424 is for R12 so not for retrofit and requires R12 service tools.
It is pre-filled with mineral oil and specific amount for NSX so again, not much point leaving POE in the system despite it's being compatible with both the mineral and PAG oil.


Kaz

 

[VancouverBCnsx]

Thanks Kaz for all your helpful comments and getting back to me so quickly.

 

[VancouverBCnsx]

I did not realize that the Denso A/C compressor was not for retrofit and set up for R12. It is the only A/C compressor that Denso lists in its catalogue (albeit from 2014) for the 1991 NSX. https://www.carid.com/images/denso/...ng/denso-ac-compressor-components-catalog.pdf
What compressor would you recommend if converting to R134a?
Thanks

Marc

 

[goldNSX]

What compressor would you recommend if converting to R134a?

You can order the one for the 93 or 94 model from Acura. It's R134a. You just have to take over the base to the hose fitting form the old one, so you don't have to change the expensive hoses as well. That's what I did.

 

[VancouverBCnsx]

You can order the one for the 93 or 94 model from Acura. It's R134a. You just have to take over the base to the hose fitting form the old one, so you don't have to change the expensive hoses as well. That's what I did.

Is the Denso 4711194 the model you installed? Not sure that I understand what you mean by "take over the base to the hose fitting from the old one".

Did you consider the GPD 6511599 or the 4 season 68366 compressors as well?

Thanks

 

[goldNSX]

Is the Denso 4711194 the model you installed? Not sure that I understand what you mean by "take over the base to the hose fitting from the old one".

I was ordering from the Acura parts catalog. Not sure what Denso no. it is.

The base on top of the compressor can be seen as part no. 8 here: https://www.oemacuraparts.com/auto-...dy-air-conditioning-cat/a-c-compressor-2-scat You don't have to order it, you just have to take it over from your old compressor if you keep the old discharge and suction hoses.

 

[Kaz-kzukNA1]

Hi, Marc.

The compressor oil circulates through the entire a/c system via refrigerant.
Therefore, if you are converting to R134a, you will be forced to use different oil spec from R12 mineral oil and thus, better to use new R134a compressor filled with proper oil designed for R134a usage.

By the way, this is the reason why you should disable your compressor if your refrigerant level is very low.
The oil can't return to the suction port of the compressor and thus, low oil level yet the compressor keeps spinning despite the triple pressure switch that meant to disable the compressor at extremely high/low pressure condition.
It will only disable the compressor when the refrigerant is really low but by that time, it could be too late.

Recently, one UK owner contacted me with his a/c issue and his system only had 140g left in the system yet the compressor kept engaging.
Glad he reacted early enough before splashing metal flakes from the compressor.
He now has good a/c again.


If you want the OEM R134a compressor, go for the P9K spec. Parts #38810-P9K-E01 .
Manufactured by Denso and shared among several Honda models.

Much quieter and improved friction loss than the original R134a compressor fitted to earlier models.
This is the one I used for my A/C Refresh.

It is much more expensive than the aftermarket one and it does not come with the new pulley/clutch/pressure plate/field coil so you must re-use your existing one (if it's not the cause of your noise) or get new assy.


If going for the aftermarket one, since OEM is by Denso, I don't see the point of selecting other brands.
Denso compressor is one of the most reliable and durable model out on the market.


One of the benefit of going for the aftermarket compressor is that you will get not only the compressor body but also the pulley/clutch/pressure plate/field coil included at significantly cheaper price than the OEM P9K one.
Remember, P9K is only the compressor body and those are not included.


Please note that the information on densoautoparts.com is not correct for some of the year models (mainly for the geometry offset of the compressor bracket and the pulley from 97+ models) so please be careful when selecting the aftermarket compressor.

Here in UK, I know several owners bought Denso compressor #471-1193 and #471-1194 .
Please note that I never installed these two aftermarket models by myself so I can't confirm the following information based on my own experience.

The difference between the two models seemed to be only the pulley/clutch area (diameter/offset) and the compressor body itself seemed to be the same.

#471-1194 is for the R134a up to 96 NSX.
However, for some reason, Denso fitted smaller diameter pulley/clutch (about 125mm) for this -1194 that you may need to find alternative smaller a/c belt.
Without it, you may not be able to achieve the ideal belt tension with the existing adjuster.

Not a problem if you are planning to transfer your existing pulley/clutch/pressure plate/field coil on this new compressor.


#471-1193 is for the R134a on 97+ NSX although densoautoparts website doesn't show it like that.
Honda modified the design of compressor bracket attached to the eng block for 97+ MT/AT models.

This will shift the compressor body towards the right wheel yet the crank pulley and idle pulley position didn't change.
In order to compensate for the changes in geometry, Honda also changed the offset of the pulley/clutch on OEM compressor.

With -1193, it will have the correct pulley offset when used together with 97+ bracket.
Also, it comes with larger diameter pulley (and thus, can use existing belt/adjuster) of about 140mm compared to -1194.

Again, you could use this one if you are planning to transfer your existing pulley/clutch/pressure plate/field coil on this compressor.

Or, if you have aftermarket header and want to shift the compressor body away from the front header (but the difference is very small that it may not worth it unless you can find used bracket), then you can use this compressor without transferring your existing pulley assy and just replace the bracket to the 97+ spec although the new one is fairly expensive (for the price, you can buy another new aftermarket compressor….).

What goldnsx mentioned is this;

When you get the new compressor, it will be delivered like this.
(Please note that this is OEM Denso P9K compressor so it doesn't include the pulley assy. With the aftermarket Denso one, it does.)
The yellow marked parts is the shipping plate.

When you remove your existing compressor, it will look like this.
The blue marked parts is the service plate/valve.
Mine is R134a from the factory so the label and appearance (safety valve) would be different from your R12 one but the idea is the same.

So, as you can see, before you install the new compressor, you must swap the yellow and blue parts.

Please note that under the service plate, there is an octagonal shape seal.
You must install new one on the new compressor.

With the aftermarket Denso compressor, you should find new one in the bag inside the box.
However, with OEM P9K one, it doesn't include it so please get it (38839-PR7-A01) in advance.
Not expensive any way and you can find aftermarket one as well.

The PAG oil used on R134a system absorb moisture really quickly so same for the drier, deal with it at the very last moment just before the evacuation of the system.

Good luck!

Kaz

 

[goldNSX]

Honda modified the design of compressor bracket attached to the eng block for 97+ MT/AT models.

This will shift the compressor body towards the right wheel yet the crank pulley and idle pulley position didn't change.
In order to compensate for the changes in geometry, Honda also changed the offset of the pulley/clutch on OEM compressor.

Years later, you gave me the explanation for this redesign. I had to modify the 97+ header shield a little bit with the old bracket of the A/C compressor.

 

[angus]

If you don't use the A/C and it isn't making noise when you have it off, then why not just avoid using it anymore? You could also unplug the one wire to the clutch to prevent it coming on with the defrost.

 

[VancouverBCnsx]

Thanks for all the help.
Unfortunately , I have not found anyone in the Vancouver area so far who has the expensive setup to extract the R12. Many are currently only dealing with R134a

 

[VancouverBCnsx]

Thanks for all the help.
Unfortunately , I have not found anyone in the Vancouver area so far who has the expensive setup to extract the R12. Many are currently only dealing with R134a

Just not using it would be an option except for the impact on the effectiveness of the defrost/defog function and possible further corrosion of the fittings.

 

[goldNSX]

If R12 stations are getting rare that's a good reason to switch to R134a. My guess is that you can go for R134a easily in Canada regarding effectiveness. The later arguement counts in very hot climates.

 

[The King]

We sold our Honda store a year ago. We still had the gear to work on R12 at that point. I'm pretty sure that hasn't changed. Maybe check a local Honda shop, as they may be able to help you.