A/C service

[nigel]

I can’t remember, I’m gonna do an a/c evacuation, replace the filter drier and charge and I’m gonna put in some fluorescent dye and I forget where to put it in. Anyone ? I’m thinking in the high pressure port where you attach the high pressure hose before I do the evacuation ?
Anyone, please so I don’t screw it up.

Cheers
nigel

 

[Kaz-kzukNA1]

The dye travels the entire system by bonding to the refrigerant.
You have empty system and going to open it any way so there are many options available.

The method and when to add the dye depends on the type of the dye you have and how you re-charge the system.
For example, you may have just the dye in a small container or you may have refrigerant service can that contains the dye/oil as well.

NSX A/C system has such long travel distance that you can add the dye at different location depending on how you charge the refrigerant.

Unless you have all the equipment, just visit the A/C specialist with the expensive A/C service station.
Ask if it can back flush the entire system using the actual refrigerant.
Most likely, they will remove both shrader valves from the service ports before flushing and then install new valves so one of the most common place for the leakage is already dealt with.

This type of service station can also recover the old system oil so no guess work involved when adding the fresh oil.
It can even add the dye if you request for it.
Pretty much everything is automatic so cost effective if you don't have all the equipment.

Regardless of A/C service station or doing DIY, first thing first.

Put the car inside the dark garage and use UV light to look for the trace of old dye from the past.
You don't want getting wrong leak detection due to previous leakage or splashed dye in the past.
Just clean the trace of old dye.
For this reason, I prefer not to add the dye until the leak is confirmed by other method but it's just me.

If doing DIY and since you are disturbing the system, probably easier to inject/pour the dye through the suction/low side service port before pulling the deep vaccum.
The pipe points towards the floor so the dye will run down along the pipe and stays there until you re-charge the system.
Once the system re-charged and compressor engaged, it will travel all around the system via refrigerant.

There are other methods available depending on what equipment/parts you have.

Hope you won't see any leakage at the evaporator….


Kaz

 

[nigel]

Thanks Kaz, I’ll just add a small bottle of dye at the low pressure port by removing and replacing the valve core and then do the deep vacuum, then add the correct amount of R-134 however much that is.
Any idea how much R-134 I should add to get the correct reading on the gages for 90 deg outside air temp ?

Cheers
nigel

 

[Kaz-kzukNA1]

Double post seemed to be on the rise again for some reason.....
Any way.....

For US model, there should be A/C spec label somewhere under the bonnet/hood.
Or, probably you are asking because your NSX originally had the R12 system???

If you use the A/C service station, our NSX is already in the database but for the R134a NSX, the amount of refrigerant is 800g (Min) - 850g (Max).

The receiver/drier acts as the accumulator as well so if using much larger tank capacity, there is a small window for the mistake but never overcharge it.
Otherwise, you could puncture the evaporator.

The amount of total system oil for R134a (ND-OIL8) is 160ml (Min) - 180ml (Max).

If replacing just the drier, you would need to add small amount of oil if not using the A/C service station that can recover all of the old oil or manually flushing the entire system.
As mentioned above, it will involve guessing work because you won't know how much oil was lost if you had leakage in the past.

These spec are in the workshop manual and also you should be able to find the English version of performance chart for NSX A/C system in there as well.


Kaz

 

[crxguy52]

Not to hijack this thread, but I’ve got a similar question. I’m replacing the old r12 compressor with a new Denso unit, and the FSM says to remove oil from the new compressor: 80ml - (ml removed from old compressor).

Almost no oil came out of the old compressor - like one drop. That would indicate that I should drain almost all of the oil (80ml) from the new compressor, minus 10ml for the accumulator I’m replacing as well. Is this common with NSXs? I just don’t want to drain all the oil and fry the new compressor.

For what it’s worth there’s not a big leak in the system - the refrigerant leak is the o-ring between the evaporator and one of the lines. The condensers are intact and not leaking.

 

[Honcho]

Not to hijack this thread, but I’ve got a similar question. I’m replacing the old r12 compressor with a new Denso unit, and the FSM says to remove oil from the new compressor: 80ml - (ml removed from old compressor).

Almost no oil came out of the old compressor - like one drop. That would indicate that I should drain almost all of the oil (80ml) from the new compressor, minus 10ml for the accumulator I’m replacing as well. Is this common with NSXs? I just don’t want to drain all the oil and fry the new compressor.

For what it’s worth there’s not a big leak in the system - the refrigerant leak is the o-ring between the evaporator and one of the lines. The condensers are intact and not leaking.

It's gonna be tricky because you won't know how much oil is left in the rest of the system. The new compressor is filled with the correct amount of oil for the entire system, not just the compressor. So, you either have to use a DIY flush kit and flush the rest of the components and lines (good time to replace the O-rings with R134 compatible ones), or take it to a shop that has the big machine that can evacuate all of the old oil from the system. Then, take the car home (with the A/C compressor fuse pulled OUT) and swap the new compressor in. Fill with 800-850 g of R134 and you should be good to go. See below explanation from Kaz:

http://www.nsxprime.com/forum/showthread.php/213061-Replacing-A-C-Compressor-Oil

 

[Kaz-kzukNA1]

Not to hijack this thread, but I’ve got a similar question. I’m replacing the old r12 compressor with a new Denso unit, and the FSM says to remove oil from the new compressor: 80ml - (ml removed from old compressor).

Almost no oil came out of the old compressor - like one drop. That would indicate that I should drain almost all of the oil (80ml) from the new compressor, minus 10ml for the accumulator I’m replacing as well. Is this common with NSXs? I just don’t want to drain all the oil and fry the new compressor.

For what it’s worth there’s not a big leak in the system - the refrigerant leak is the o-ring between the evaporator and one of the lines. The condensers are intact and not leaking.

As you stayed with the R12 compressor, don't know the current system configuration described below and the reason for replacing the compressor.

You are using R12 compressor because;
1. you stayed with the R12 refrigerant and thus using mineral oil ND-OIL6.
2. the system was retrofitted to R134a with ND-OIL8 (PAG) and kept using the R12 compressor.
3. using alternative refrigerant such as RS24 with mineral/synthetic oil and kept using the R12 compressor.

You are replacing the compressor to the new Denso one prefilled with the total system amount of;
a) mineral oil (R12)
b) ND-OIL8 (R134a)

First, the information in the original workshop manual is wrong.

The information you have (80cc - wrong) is for the R12 mineral oil and that is the wrong info.
Should have been 120 - 130cc of R12 mineral oil instead.

For your reference, for the R134a ND-OIL8 (PAG), the total system amount is 160cc - 180cc max.

You should not drain more than 50cc from the new compressor but, and this is a big but.


Because you lost so much refrigerant that the oil couldn't return back to the compressor, you just don't know how much oil is left in the system or even what type of oil.

Fair amount of oil could have leaked to the outside world if the refrigerant was leaking.

You stated that 'For what it’s worth there’s not a big leak in the system' - and this is the problem.
Even when the car is parked, the system is under pressure that you are losing the oil all the time.

Please remember that the compressor oil travels all around the system by bonding/mixing with the refrigerant.

Thus, the 'guessing work' as mentioned in my post.

You may have certain amount of oil left inside the system and it could be combination of mineral, PAG, POA oil depending on what was done in the past.

On top of these, you don't know how much contamination you have inside the system.
Because you only saw one drop of oil out of the compressor, you may have burnt oil left in the system, contaminated with the moisture, oxidised, etc.

If the refrigerant leaked in the past, don't know the full a/c service history and getting new compressor, don't bother with the oil balancing.

Just have your system flushed.

Many compressor manufacture won't warranty your new compressor unless required processes were followed.
This will also include but not limited to replacing the drier/receiver and the exp. valve at the same time.

Kaz

 

[Big McLargeHuge]

I'll add that during my R12 to R134a conversion, I had the same situation where no oil drained out of the old compressor. I flushed out all the lines manually and replaced all the system O-rings, everything except for the evaporator (which now also might be leaking...). The lines were very clean, the dirtiest by far was flushing the front two condensers which had a lot of junk inside, so I think that's where much of the old oil ends up collecting. The evap would also retain some old oil unless it was well flushed which is hard to do by hand. Since you should be changing the receiver/drier there would be no old oil holdup there. My new Denso compressor came with about 110mL of oil included which I used plus a bit of new UV dye.

 

[crxguy52]

Thanks for the responses everyone. To clarify, I am replacing the original r12 compressor with one of the newer r134a denso compressors because I had to evacuate the system fix a leaking o-ring. The compressor has been a little noisy since I bought the car and it was cheap enough to replace while I had the system empty. I’m also replacing the idler pulley bearing.

Given that I don’t know how much oil is in the system, and whatever is left is the r12 (mineral) oil and I’m converting to r134a, I’ll go ahead and flush the system while I’ve got it apart. What solvent do you recommend? I would imagine alcohol would work well as it does not leave a residue. I’ve got access to pure ethanol, I’m thinking that should work.

 

[drew]

a/c flush solvent is pretty commonly available, though I suppose IRL a bottle of isopropyl will work ok.

However, the google says: "An airconditioning system flush solvent is prepared by mixing 60-70% heptane with 29-40% isopropyl alcohol and up to 1% fragrance."

Though, I'm not convinced that the fragrance is absolutely necessary.

***

The big issue is to look for the "black death" and/or shavings in the system. Before one starts use a rag to wipe the insides of the pipes on either side of the compressor to look for residue or debris for a baseline...and then flush the system.

Adding in extra oil is easy, but removing it is hard. FYI: The expansion valve can be replaced WITHOUT removing the dash, but it is super tight quarters.

 

[Kaz-kzukNA1]

[MENTION=18814]crxguy52[/MENTION], if you are in US, just get the 4Seasons Dura Flush. Proven and works well.
Although non-flammable, no longer allowed to be shipped as air cargo.

Unless you are removing the exp valve or disabling the centre needle, you can't flush through the evaporator using DIY method.
Another benefit of flushing using the ac service station as it uses the actual refrigerant so exp valve can stay as it is.

Kaz

 

[Big McLargeHuge]

Yep I used Four Seasons 69994 and it worked well, seemed to be good at cleaning and readily evaporated but I also blew out the line afterwards with air. Get at least 3 of the 32oz cans for the whole system if not 4, it gets used up quickly.

 

[crxguy52]

Thanks for the advice everyone, I'll get some AC flush on order