Air Conditioning Compressor 1991 NSX

[Formula 91]

Hi Guys,

I need a new compressor. I checked the price at Honda and nearly had a heart attack (£1700 ).Any ideas on where to purchase a compressor , expansion valve and receiver at sensible prices .

Ricky

[NSXGB]

Hi Guys,

I need a new compressor. I checked the price at Honda and nearly had a heart attack (£1700 ).Any ideas on where to purchase a compressor , expansion valve and receiver at sensible prices .

Ricky

Try RockAuto in the USA.

[Formula 91]

Thanks for the reply .I have checked there website and I am impressed with the prices including delivery to the UK. Do the american parts fit okay and am I better going for a new part rather than a reconditioned compressor . Also anybody any idea how many hours it takes for fitting the parts at a garage.

[lotusolly]

I replaced mine with a Denso remanufactured unit from Rockauto and had no problems.
Kaz has mentioned previously that there are a couple of different versions which vary on the load that they put on the engine. If you search on here you should be able to find his post regarding this.
The only other thing you need to bear in mind is that the pulley size is different on US spec units and you will need a different size belt,. When I next go to the car I will check the size for you and post it up. The correct size one was only about £7 from my local motor factors.

Olly

[nigel]

You can replace it with a Honda Legend compressor and switch the NSX pulley to the Legend one for a great savings and have a new Honda compressor.

Cheers
nigel

[Formula 91]

Thanks for the replies . I think I will go for the Denso Compressor as well .Anybody any idea on fitting times for the repair as it looks like it may be a nightmare to install the new part .

Ricky

[Hagasan]

If my memory serves me correctly the Denso compressor on our cars is a common part. I don't have the part no. at hand but I know it's the same one used on a Porsche 964. The differences will be the service ports the pipes connect to and the clutch/pulley. The NSX has I think two different pulleys that stick out from the body different distances.

You may be able to find a cheap Denso unit and swap over the service port and pulley assembly. Just find out the Denso part no. Google it and see what other cars it's fitted too.. Sometimes the same part can be priced with a huge variance depending on what car you buy it for!!

[Kaz-kzukNA1]

Based on your old post, I believe your NSX is 91 spec and thus, came with the R12 A/C system.
The expensive price you mentioned is probably for the PR7/PW0 R12 spec compressor that is very likely to be discontinued outside of Japan by now.

Not sure whether your A/C system is already converted to R134a, later spec or not but if your compressor has failed, just get P9K R134a spec OEM compressor (manufactured by Denso, shared with Integra, NSX, etc) or equivalent Denso remanufactured one and retro fit the R134a conversion kit.
The Denso compressor design spec is 10PA15C type so any compressor based on this has the same body shape.

From the Eng power loss and A/C efficiency point of view, R12 system is better than the R134a one so there are owners still using the R12 system on their NSX in Japan but the gas itself is getting expensive every year…..

Strictly speaking, you should replace the o-ring when converting to R134a spec from R12 but even during the NSX Refresh plan at Honda factory, they won’t replace it when doing the conversion.


I touched on A/C system on NSX Prime and NSXCB several times so please read them together with the info in this post;
http://www.nsxcb.co.uk/entry.php?1319-R12-and-R134a-A-C

http://www.nsxcb.co.uk/showthread.php?11926-Aircon-pump&p=107062#post107062

http://www.nsxcb.co.uk/showthread.php?11364-A-C-Compressor&p=103938#post103938


You need to be aware that the diameter of the R12 spec receiver is larger than the R134a one so if you decide to use the R134a receiver on 91 model, you will need to replace the holder bracket as well or make small modification to your existing one.
The basic concept of the receiver feature is the same between the R12 and the R134a but the R134a one has better internal filtration design if you cut through and inspect it.
However, for the extra capacity and due to the bracket difference above, many 91 model owners are still using the R12 spec receiver even after converting to R134a gas.

As mentioned above and in the above links, the compressor body dimension is the same regardless of R12/R134a or even other Honda models or year models.
You just need to keep the correct combination of the A/C compressor CL/pulley and the compressor mounting bracket on the Eng block.
The bracket was changed from 97+.

If your CL/pulley on your existing compressor is fine, then just get new P9K spec compressor or re-man one and reuse the CL/pulley from your old compressor.
If you are using the aftermarket header on your 91 model, it would be good excuse to spend extra and get the 97+ mounting bracket to shift the compressor away from the header against the radiant heat.



Replacing the compressor is not too bad.
Mainly, you just need to remove the U-shaped stiffener at the bottom of the eng/gbox assy and then remove the grey front cross beam to get access to the compressor.
Honda will charge you about 2.7Hr including the discharge/charge of A/C gas.

The receiver depends on the type and what you are going to do with the receiver bracket but in general, you will be quoted 1.2Hr excluding the discharge/charge of A/C gas (already included in the compressor labour charge of 2.7Hr).


Now the biggest challenge would be the expansion valve.

There are R12 and R134a spec valve and despite the different operating pressure, R12 spec one works even after converting to the R134a gas. You should replace it if breaking the pipe connection together with the receiver.

If the fitting at the valve can be loosened without any issues, you are very lucky.

Over the years, quite often, the soft aluminium fitting is seized onto the expansion valve thread and even with the use of double wrench, if you damage the fitting (that is part of the evaporator), you will be forced to take the dashboard out (the big cabin surrounding parts in front of the driver and passenger seat) to replace the evaporator and that’s a huge task.

Because of this, in Japan, we don’t touch the expansion valve without first getting the owner’s consent that there is a high risk of damaging the evaporator fitting when replacing the expansion valve and thus, it could result in taking the dashboard out in order to replace the evaporator. Expanison valve comes with the new evaporator unit.

You can access the expansion valve by removing the blower motor fan housing under the bonnet so it will be about 2.0Hr to replace the valve if the fitting is not seized.
If you were quoted more than 6.5 – 6.9Hr, that means they are going to remove the dashboard so ask them to try the blower motor fan method first.
The Honda labour charge system only shows the procedure of replacing the expansion valve by taking the dashboard out…..

If the dashboard is coming out, you may want to replace the evaporator anyway. It’s sided (RHD, LHD) so make sure to order the correct spec if ordering the evaporator. There are reasonably priced aftermarket evaporators available for LHD NSX but not sure for the RHD onel.....

In Japan, we normally replace the whole heater unit as an assy (evaporator, heater core, control actuators, white big housing, etc) because there were several reports of coolant leakage from the heater core and good refresh of electronics drivers as well.


Kaz

[Formula 91]

Hi ,Thanks for all the replies. The parts are on the way from Rock Auto .

Ricky

[greenberet]

If you are using the aftermarket header on your 91 model, it would be good excuse to spend extra and get the 97+ mounting bracket to shift the compressor away from the header against the radiant heat.

Looking at the US parts catalog at oemacuraparts.com, it seems that the R12 compressor (part number 38810-PR7-A01) was only used in US NSXs for the 1991 and 1992 model years. It looks like the R134a compressor (part number 38810-P9K-E01) was introduced for the 1993 model year and was used until production ended in 2005.

Interestingly, the bracket that holds the compressor to the engine block was not changed in 1993 along with the compressor, but only in 1997. As of that year, both manual transmission (now 3.2 liter) and automatic transmission (still 3.0 liter) cars switched from the earlier compressor bracket (part number 38930-PR7-A00) to the later bracket (part number 38930-PR7-A01).

Since the earlier bracket was installed with the later compressor at the factory, since the later bracket was installed on both 3.0 and 3.2 liter engines, and since you can use the same belt with any combination of compressor and bracket, how exactly did the design of the bracket change? It couldn't have shifted the compressor away from the header by moving it towards the right of the car because Honda never changed the part numbers of the crankshaft pulley and tensioner. Does the new bracket shift the compressor away from the header by moving it a bit further towards the nose of the car, requiring that the tensioner be backed off slightly?

[Kaz-kzukNA1]

Hi, greenberet.
I think you got confused by the superseded parts no..

Until 1997, all NSX left the factory with PR7 spec compressor regardless of the R12 or R134a system used.

There are at least 3 different PR7 spec compressors available (one of them only used on certain VIN range of Type-R) and those are the ones used up to and including the 1996 models.
The P9K spec compressor was only introduced in 1997 for the NSX (together with the later spec bracket) and it superseded all of the previous PR7 R134a spec compressors apart from the R12 one, obviously.

So, if you just look up the parts system, the P9K compressor will be displayed for the pre-97 NSX that left the factory with the R134a gas.

As mentioned, the compressor body dimension is the same regardless of R12/R134a spec, PR7/P9K, year model, etc, etc.
You just need to keep the correct combination between the CL/Pulley and the Bracket.

Because the body dimension is the same, if the bracket shifted the compressor outward towards the RR wheel arch, you need to change something further, as you stated correctly that the crank pulley and the A/C idle pulley geometry haven’t changed.

Hence, Honda made the changes at the CL/Pulley design on P9K compressor.


https://lh4.googleusercontent.com/-J5rQlg6m874/VRqlkvAXdZI/AAAAAAAAYgE/sMPWP8cM26k/s640/img_001.jpg https://lh4.googleusercontent.com/-ejjqvkfE1_Y/VRqllIrhrHI/AAAAAAAAYgM/UHICv7jwils/s640/img_002.jpg
CL/Pulley on P9K spec at the left and the ones on the PR7 spec at the right.
As you can see, the edge of the A/C belt is much closer to the face of the compressor body on the P9K.


So, this is the reason why you need to keep the correct combination between the CL/Pulley and the Bracket because the compressor body dimension is the same.

In fact, if you order the OEM one, it doesn't come with the CL/pulley so you will be forced to re-use the existing parts any way unless you pay the extra for the additional parts.
I have never ordered one but I believe the remanufactured Denso one will come with the CL/pulley.

Kaz

[Button]

Kaz, as always very helpful information. I have read a number of previous posts relating to the compressor and R12 to R134a conversion. These indicated that if continuing to use the PR7 compressor this would likely soon fail after conversion to the new gas.
On the basis the PR7 compressor was used / supplied by Honda until 1997 as a R134a system why is it not acceptable (good practice) to continue to use the original compressor? Many thanks

[Kaz-kzukNA1]

Hi, Button.
Not sure I understood the point of your question especially the term ‘original compressor’ so I will answer based on two different points.

If your question is related to the usage of PR7 compressor on R12 as well as on R134a system, then please note that there are two major differences among the PR7 compressors.
One for the R12 and the other one for the R134a system. There are also minor differences within the R134a PR7 compressors but I’ll leave them for now.

Based on so many conversion (R12 to R134a) done in Japan (you don’t want to drive a car without A/C in Japan, so hot and humid, one of the reason why even Type-R/NSX-R owners install the A/C), it is safe to say that if R12 PR7 compressor was kept using with R134a gas after the conversion, sooner or later, it will fail requiring another A/C service.

Addition to the new compressor, you will need to replace at least the receiver/drier again that was already replaced at the time of conversion so waste of money for the parts/labour.

Also, many owners tend to leave the sign of compressor failure until it gets really noisy that by the time the system was opened, lots of metal flakes were stuck inside the condenser causing another expensive repair.
Please remember, the receiver/drier is located after the condensers.

So, knowing that the R12 PR7 compressor will fail in the future after the conversion and for the prevention of serious expensive repair, instead of duplicating the same tasks, it is always recommended to replace the compressor to the latest R134a spec one (P9K spec for our NSX) at the time of conversion. Needless to say, you are going to disturb the system connection so you must replace the receiver/drier (and the expansion valve).



If your point of question is why it is better to use P9K compressor (only R134a spec available) instead of R134a PR7 one, then please keep reading below. Otherwise, please ignore it.

Nothing wrong by keep using the R134a PR7 compressor until it fails but you will notice much higher friction (eng power loss) when PR7 comp was engaged than the P9K one.

When you drove R12 PR7 compressor equipped NSX (mainly 91 model some 92 one), you won’t notice too much power loss when the A/C was engaged.
However, after the introduction of R134a PR7 comp, you would notice some eng power loss under the same condition.
P9K comp has improved friction loss and thus, it won’t eat up eng power like the R134a PR7 comp.


If your R134a PR7 comp started sounding bit louder than it used to be, best to act early before it turns into grinding noise. You don’t want to let metal flakes inside the A/C pipe system and most importantly, block the condensor…
Quite often, when you replace the compressor to a new one, you will be amazed how quiet it can be when the A/C has engaged.


Hope I answered at least part of your question…..

Kaz

[goldnsx]

When I changed my old A/C compressor of my 91 I went with new parts from a 94.
- new compressor
- new stator
- new clutch
- new receiver R134a with new bracket (Kaz metioned above) (R134a is not compatible with R12 receiver chemicals)
- new o-rings (except at the expansion valve, kaz explained why), there is a R12 and a R134a version, watch out for this difference.
- new valves IN/OUT, you don't need to buy the hole pipe because of a £0.1 part
- biggest problem of all: how much oil (R134a) has to be added? It's 120-140 m. But how much did you add in the past and how much remains in the system? Wild guess. The most expensive way: flushng each component.

[greenberet]

Dear Kaz, thank you for the explanation and pictures. That's very good to know.

So in order to move the a/c compressor a few mm to the right, to gain a bit more clearance between the tubular exhaust header and the compressor, you can use the 1997+ compressor bracket (currently part number 38930-PR7-A01). Then, in order to keep all of the pulleys aligned, you also need to use the thinner 1997+ a/c compressor clutch set (currently part number 38900-PR7-A04).

Two years ago, when I installed a new a/c compressor, I ordered an R134a 38810-P9K-E01. Thankfully, I reused my compressor mounting bracket and compressor clutch set. More by dumb luck than anything else, it seems my three a/c pulleys should therefore still be aligned. Nonetheless, with the help of your pictures, I'm going to try to make sure I have a thick, earlier-specification clutch set since I believe I should still have an earlier-specification mounting bracket on my 1991.

goldnsx - when you changed your a/c compressor, it's good that the earlier clutch set was still available. According to the US parts catalog, clutch sets for the 1991-96 model years are no longer available even though the earlier mounting bracket is. If anyone buys a new clutch set today, hopefully they will make sure they use it in conjunction with the correct compressor mounting bracket.

[Button]

Greenberet i am inclined to agree with your logic reading all the posts but will defer to Kaz / others for confirmation.

Kaz thanks for your detailed answer to my query above, your 1st part fully answered my question as i have a R12 version of the PR7 compressor - i understand now with there being differing versions of the PR7.

Sorry a couple more queries

1/ reading posts am i correct in assuming you can re use the CL and pulley from the R12 PR7 and put them on the P9k?

2/ I now understand need to replace my R12 PR7 Comp on gas conversion. Has anyone now ordered and received the compressor set from Rock auto to clarify what clutch / pulley configuration it comes with? This will influence whether to consider reuse of CL and pulley ( subject to being able to or need to also get the later bracket)

Many thanks
John

[Kaz-kzukNA1]

Hi, Button.

1. Strictly speaking, the CL capacity is different between the two but when doing retro fitting using the OEM compressor, I never saw any issues for many years by re-using the R12 CL/pulley on the OEM P9K R134a compressor.

2. I think some owners bought the compressor from Rock Auto so hope they will provide some feedback.
If I remember correctly, there were 2 model no. for re-man R134a Denso compressor and I think Rock Auto (and possibly even Denso) was not listing it properly against the year model as they don’t know when the bracket was changed. If your CL/pulley assy is fine, just re-use OEM one if there is enough clearance against the compressor face.

Kaz