AC Overhaul-advice needed!

[SWFL_NSX]

Hi Crxguy52,

Yes, I used the compressor that is for 1992 r12 systems. At least I hope that rock auto sent me the right one :tongue:

 

[crxguy52]

Hi Crxguy52,

Yes, I used the compressor that is for 1992 r12 systems. At least I hope that rock auto sent me the right one :tongue:

Thanks for the info. Sooner or later the AC will need to be repaired in all older NSXs, and it's good to have the info on hand. I was thinking about what would cause a low pressure differential, and the RPM thing occurred to me at one point. Glad it was the issue!

I replaced everything in the integra with ND parts for like $300. Gotta love rockauto. FYI it ended up being cheaper to buy everything separately than the "kit" they sell, in case you go that route in the future.

 

[MrHugo]

I am trying to refresh my A/C system too because it is not cold enough anymore.... so I will post it here. (Please excuse my lack of knowledge in A/C system)

My car is 1992. Previous owner said he does not know if the system has been changed to R134a.

So I went to look at the A/C pipe and saw this:


Does that mean my car has been changed to R134a?

I am going to visit a "supposedly" very reputable A/C repair shop in Southern California "Lynn's Air" in Downey this Saturday. I want to be as educated as possible before going in.

I know R12 is more expensive but I would like to have R12 instead because the system was made for R12.

My question is:

1) if my system has been converted to R134a, would you suggest recharge it back to R12 or R134a?

2) If I recharge it back to R12, do I have to replace any parts beside full system evacuation? Maybe replace drier?

3) Should I ask the mechanic to flush my system? I am afraid they will not do it because it is a lot of work?

4) If they are truly experience, I assume I should not need to direct them how to/what to do. But should I mention any important? such as monitor oil been evacuated and refill with the same amount of oil?

 

[Kaz-kzukNA1]

Hi, MrHugo.
Probably too late and while your questions were not necessarily directed to me, in the future, if you need someone's attention, please use the 'mention' feature by adding @ marking in front of the userID so that your post have better chance of being noticed.
For example, [MENTION=23169]MrHugo[/MENTION]
Or, just send PM/email to the user.
I'm based in UK and mainly focusing on the blog on NSXCB site and browse Prime only through tapatalk so may not notice the new post or not quick to respond.


Your photo is showing the R134a retrofit adaptor over the old R12 charge valve.
R12 charge port has fitting with external thread.
R134a one uses quick coupler so there is a hollow section for the coupler to engage.
The internal thread is purely for the sealing cap.


So, your system was converted to R134a in the past.
I'm afraid from your photo, it looks as if the refrigerant and the oil are leaking from there.
The Schrader valve is one of the common place for the leakage issue.


I don't know how the conversion was done (retrofit kit containing just the valve adaptors and the PAG/POA oil, retrofit kit + new compressor or retrofit kit + new compressor + other parts replaced) so I'll only touch on the basic.


There are many early model NSX in Japan and US with their a/c converted to R134a from R12.
If the system is working fine, you would get freezing cold air from the air vent even after the conversion to R134a.

The summer in Japan is really humid and normally over 30degC (86degF).
In August, quite often, it will hit over 35degC (95degF) and from time to time, even 40degC (104degF) yet I have never heard of NSX owners going back to R12 because that's more efficient than the R134a.
There are people staying with R12 for that reason but it's simply because their R12 system is still working.
You don't want driving a car without A/C in Japan…..
It was 37degC (99 degF) today in Tokyo….


I think you are trying to fix your issue from somewhat different/wrong aspect.
So, not necessarily answering your questions but my personal view is as follows towards your question;


1. Re-charge with R12 or 134a?
As you mentioned at the very beginning of your post that your a/c system is not cold enough anymore, it suggests that it was fine in the past.
Therefore, you need to find the cause of the issue first.

You will end up with the same situation (issue) even if you recharge the system regardless of R12 or R134a.
If it was already converted to the latter, I would stick with it although I don't know how far the conversion was done.


2. If back to R12, what needs to be done?
Your R134a system would be using PAG or POE oil at the moment.
I won't go into detail but if you really want going back to R12 with mineral oil, I recommend disconnecting the compressor and drain any oil left inside and flushing the entire system though some people will tell you that it would be fine without doing these tasks especially if POE is in use.

If you have any leakage, please note that R134a + PAG + moisture is a perfect mixture for creating acid causing corrosion inside the a/c system.
Although compatible, mixing POE and the mineral oil may result in chemical reaction producing another debris causing blockage especially at the exp valve, drier, etc.

Flushing will remove the guess work of how much mineral oil to be poured if going back to R12 although some people would skip the flushing and just drain the remaining PAG/POE oil from the compressor as much as possible.

You must replace the drier any way because of trapped debris, moisture, PAG/POE oil, etc. R134a drier will absorb moisture very quickly.

You will need to remove the retrofit adaptor from the original R12 charge valves.
Make sure to replace the Schrader valve at the same time although you could be forced to do so any way depending on the type of retrofit adaptor.


3. Flush it?
As mentioned above, I recommend flushing it if you really want going back to R12.
It also depends on how the previous conversion was done and the type of oil used.
However, it may not be cost effective to go back to R12.

As you are/were taking the car to the a/c specialist, I'll leave the detail to them but you will need to consider the type of oil used at the time of retrofit (PAG or POE, I'll leave the viscosity in this discussion but very important for the compressor) and also the mineral oil left inside the system before the conversion.


4. AOB?
I would leave it to your a/c specialist.
They will first inspect the health of your existing system and then recommend you what to be done based on your budget level.
Any a/c services could result from quick and easy fix to mega expensive one especially on our NSX due to the length of the system line, parts cost, layout and evaporator being inside the heater unit.


Kaz

 

[MrHugo]

Hi, MrHugo.
Probably too late and while your questions were not necessarily directed to me, in the future, if you need someone's attention, please use the 'mention' feature by adding @ marking in front of the userID so that your post have better chance of being noticed.
For example, @MrHugo
Or, just send PM/email to the user.
I'm based in UK and mainly focusing on the blog on NSXCB site and browse Prime only through tapatalk so may not notice the new post or not quick to respond.


Your photo is showing the R134a retrofit adaptor over the old R12 charge valve.
R12 charge port has fitting with external thread.
R134a one uses quick coupler so there is a hollow section for the coupler to engage.
The internal thread is purely for the sealing cap.


So, your system was converted to R134a in the past.
I'm afraid from your photo, it looks as if the refrigerant and the oil are leaking from there.
The Schrader valve is one of the common place for the leakage issue.


I don't know how the conversion was done (retrofit kit containing just the valve adaptors and the PAG/POA oil, retrofit kit + new compressor or retrofit kit + new compressor + other parts replaced) so I'll only touch on the basic.


There are many early model NSX in Japan and US with their a/c converted to R134a from R12.
If the system is working fine, you would get freezing cold air from the air vent even after the conversion to R134a.

The summer in Japan is really humid and normally over 30degC (86degF).
In August, quite often, it will hit over 35degC (95degF) and from time to time, even 40degC (104degF) yet I have never heard of NSX owners going back to R12 because that's more efficient than the R134a.
There are people staying with R12 for that reason but it's simply because their R12 system is still working.
You don't want driving a car without A/C in Japan…..
It was 37degC (99 degF) today in Tokyo….


I think you are trying to fix your issue from somewhat different/wrong aspect.
So, not necessarily answering your questions but my personal view is as follows towards your question;


1. Re-charge with R12 or 134a?
As you mentioned at the very beginning of your post that your a/c system is not cold enough anymore, it suggests that it was fine in the past.
Therefore, you need to find the cause of the issue first.

You will end up with the same situation (issue) even if you recharge the system regardless of R12 or R134a.
If it was already converted to the latter, I would stick with it although I don't know how far the conversion was done.


2. If back to R12, what needs to be done?
Your R134a system would be using PAG or POE oil at the moment.
I won't go into detail but if you really want going back to R12 with mineral oil, I recommend disconnecting the compressor and drain any oil left inside and flushing the entire system though some people will tell you that it would be fine without doing these tasks especially if POE is in use.

If you have any leakage, please note that R134a + PAG + moisture is a perfect mixture for creating acid causing corrosion inside the a/c system.
Although compatible, mixing POE and the mineral oil may result in chemical reaction producing another debris causing blockage especially at the exp valve, drier, etc.

Flushing will remove the guess work of how much mineral oil to be poured if going back to R12 although some people would skip the flushing and just drain the remaining PAG/POE oil from the compressor as much as possible.

You must replace the drier any way because of trapped debris, moisture, PAG/POE oil, etc. R134a drier will absorb moisture very quickly.

You will need to remove the retrofit adaptor from the original R12 charge valves.
Make sure to replace the Schrader valve at the same time although you could be forced to do so any way depending on the type of retrofit adaptor.


3. Flush it?
As mentioned above, I recommend flushing it if you really want going back to R12.
It also depends on how the previous conversion was done and the type of oil used.
However, it may not be cost effective to go back to R12.

As you are/were taking the car to the a/c specialist, I'll leave the detail to them but you will need to consider the type of oil used at the time of retrofit (PAG or POE, I'll leave the viscosity in this discussion but very important for the compressor) and also the mineral oil left inside the system before the conversion.


4. AOB?
I would leave it to your a/c specialist.
They will first inspect the health of your existing system and then recommend you what to be done based on your budget level.
Any a/c services could result from quick and easy fix to mega expensive one especially on our NSX due to the length of the system line, parts cost, layout and evaporator being inside the heater unit.


Kaz

Thanks so much for the informative post.

I have went ahead and recharged it back to R134a mostly because of cost and risk of leaking again. $85.xx out the door.

The a/c specialist did not find any leaks..... so I am guessing it is leaking at a slow rate. The shop only charged me 1 pounds of freon because he said there is half a pound inside already.

I wanted them to flush the system before refilling with R134a but it was too late. I am not very familiar with the mixture freon and oil, but from reading your posts and other forums, logic tells me system will run better when fully flushed and refill. Just like basketball, it is better to deflate all the way then inflate for best results.

Long story short, my a/c is now cold again mostly on the freeway because one of my condenser fan is out. Now, I just need to figure how to replace the motor without removing the bumper..... any insight?
[MENTION=25737]Kaz-kzukNA1[/MENTION]

 

[goldNSX]

A black roof with black interior contribute a lot to the A/C cooling demands. That's why you're find differences between R12 and R134a. R134a also came with bigger condensors.

You should be able to work from the wheel well to change the electric motor. But I'd check the fuse first.

 

[Kaz-kzukNA1]

[MENTION=23169]MrHugo[/MENTION], glad that at least you are now getting some satisfactory results under certain conditions.

If the Schrader valves were not replaced, please make sure to fit the sealing cap at the Hi/Lo charging ports as yours looked already leaking from there.

Not sure of the total amount of the refrigerant in your system but it depends on the size of the drier.
It acts as the accumulator.
As long as you didn't overfill, you would be fine.
You will notice lots and lots of bubbles at the site glass if there is no longer enough liquid refrigerant arriving at the drier.

If one of the condenser fan was not working, then you won't be able to 'condense' the high pressure gas back into liquid before arriving at the drier and thus, you will lose the efficiency as some of the refrigerant will enter the exp valve in the form of gas rather than the liquid.
Please check the 2 x 10A fuse for the R&L condenser fans inside the pentagonal box under the bonnet/hood.

I have replaced the condenser fan motor several times without removing the front bumper but it's not an easy task.
Unless it's my NSX, I prefer not removing the front bumper because even when placing all the shims back in place, depending on how you tighten all the bolts and nuts,
it will change the alignment of the bumper against other panels and takes long time for the adjustment.

You can access the motor from behind by removing the wheel arch liner and the meshed cover.
However, you are going to have fun if the long bolt passing through the shaft/collar holding the front/rear shrouds and the nuts are already corroded.


Kaz

 

[Kaz-kzukNA1]

........................ One other mystery-I am now getting some steam/condensation from the center vent when the compressor cycles off and i have the in-car temp set below 72-73. Unsure what this indicates.

[MENTION=33404]SWFL_NSX[/MENTION]
You are visualising how the evaporator removes the humidity from the air.
Basically, you have high humidity air getting in contact with the cold air that came through the evaporator.

Experienced many times when starting the car with a/c setting at max cold first thing in the morning on leaving the hotel in Malaysia.
The cabin was full of moisture from the tropical shower every day.

You won't have that amount of humidity inside the cabin especially if you were running the a/c for a while so you need to find out where the humidity was coming from.

Please check that the drain tube is not blocked. This is from my RHD model so different from yours but you can get the idea.
If you operate the a/c with all doors open, you should see water running down the tube and building up the puddle of water fairly quickly under the car below the steering rack.

If not, you are very likely to have this…. This one is from LHD model.

Also, you may be allowing external air entering the cabin through the deteriorated sponge seals near the firewall, behind the blower motor, etc but it's not easy directing these air towards the centre vent so I would first check the drain tube.

Hmmm...good point about the hoses, I hadn't considered. How much refrigerant would stay in the hoses, and would it have an effect?

Every time when you charge the system or just hook up the gauge to check the pressure, some refrigerant will be left inside the charge hose.
This depends on the diameter and length of the hose.
If you ask the manufacture, they will tell you the typical figure at certain temperature.

Most of the expensive a/c service stations (machine) seemed to take these into consideration when calculating the weight of refrigerant charged into the system.

My charge hose will contain 20 -21g per 1m at 20degC.

Not a big issue with our NSX as it has huge capacity drier (acting as accumulator).
As long as you charged the system with enough refrigerant (but never overcharge), it has enough 'reserve' for quite sometime.



Hope you are enjoying the nice a/c.
Here in UK, we need some of the heat from your area…. Too cold this summer….



Kaz

 

[SWFL_NSX]

After re-running the AC test at 1500rpm all values are now within 10% on the service manual test chart-I'm calling this one fixed. Quick notes:

1. I believe the vapor was a one time occurrence, possibly from a partially blocked evap hose. I have not been able to re-create it, despite identical driving conditions (daily commute).

2. The compressor is so much quieter, and there is so much less drag on the engine now!

If your compressor is noisy, change it now, not later! I did a post-mortem on the old compressor and found some wear and slight corrosion, but no metal flakes or chipping (see below) There was no metal shards in the compressor itself, and nothing in the oil that I flushed from the pipes. It appears that bigger problems can be avoided if the AC compressor is changed, even thought it may be noisy.





3. There are a wide variety of AC flush methods, kits and fluids on the market. Because I stayed with r-12, I used a flush gun connected to my compressor and mineral spirits as the fluid. For NSX specific advice it should be noted that I backflushed through both condensors, and well as the pipes to and from the compressor. For more information on flushing than you probably want to know, go to http://www.ackits.com/ in the flushing section and read all the different methods that the professionals have tried and use.

4. Disassembly and reassembly was smooth with the exception of the bolt that connects the front engine mount to the front brace. This bolt should be approached through the left rear wheel well (after removing the wheel). The SM says it should be replaced with a new one, so have one on hand before you start the job. All torque measures are in the manual but you may have to hunt for them.

Thanks again to Kaz, GoldNSX and the rest of the NSX community. The forums were a major reason I went with the NSX instead of a P-car, and this thread is a great example.

 

[bonhamsurf]

I'm trying to find the part number for the compressor on my 1991. Does anyone know what it is please?
Thanks

Sent from my SM-G973U using Tapatalk

 

[Honcho]

I'm trying to find the part number for the compressor on my 1991. Does anyone know what it is please?
Thanks

Sent from my SM-G973U using Tapatalk

The original part number for your 1991 compressor is 38810-PR7-A01, but it is discontinued because it is designed to use R12 refrigerant. Thus, you should replace it with the updated R134a refrigerant compressor, which is 38810-P9K-E01. Hopefully [MENTION=25737]Kaz-kzukNA1[/MENTION] can chime in here, because I understand from reading his blog that there are pulley and bracket differences between the old and newer compressors on the NSX.

 

[goldNSX]

If you can't find the 91 A/C compressor take the 94 version. No need to change anything if you buy OEM parts. Also buy the later version of the drier + bracket. Pros also change several o-ring, not because of possible incompability but mainly due to their age. New Schrader valves can be found in China.

Changes are 97+ because of the new 'header' (or whatever Honda likes to call it). They moved the unit about 1/2 inch to the right (new mounting brackets), so the clutch/pulley has also been changed to put them inline again.

 

[Kaz-kzukNA1]

This; http://www.nsxprime.com/forum/showt...ith-a-94-or-newer/page2?p=1996629#post1996629