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R134a Capacity

C

Cincinnati Scott

Registered Member
Joined
25 February 2006
Messages
92
Location
Cincinnati, OH
I just got around to replacing my compressor, clutch, and dryer this past weekend, but I have a question about how much r134a is the right amount. The factory manual I have gives the quantity for r12, and I've read that it's about 80% less to use r134.

Anybody know for certain? Thanks, sorry if this is oft discussed (I STFM and STFA and didn't find much help).

Scott
 
Cincinnati Scott said:
I just got around to replacing my compressor, clutch, and dryer this past weekend, but I have a question about how much r134a is the right amount. The factory manual I have gives the quantity for r12, and I've read that it's about 80% less to use r134.

Anybody know for certain? Thanks, sorry if this is oft discussed (I STFM and STFA and didn't find much help).

Scott
Click to expand...

Scott,

One of my best friends is an A/C guy and the takes car of all my cars so I have seem him add R-134 to many times.

At the front of your car there is a receiver. Looks like a silver round soda can that comes to a point at the top with a little glass "eye" and 2 metal hoses on each side. The receiver is located in the center near your washer fluid filler cap. Since the receiver has the glass eye ... guages are usually not needed. When my friends gets a car like my M3 that does not have a glass eye, then the guage comes in handy.

When adding R-134 to your car ... the AC on full (MAX), blower on high, recirculating air etc. Look at the little glass "Eye" and it will most likely look cloudy / milky. Open the valve to add R-134 and when the eye clears up your system is full.

Hope this makes sense. I just did this with him on my NSX about three weeks ago! Super cold air now!

Good luck!

Darrin
 
The eye glass on the receiver is not acurate at all. The best method is to evacuate and refill with the needed amount of refrigerant and this amount is what the OP was asking. :wink: The SM states 950 gramms of R12. I've heard two opposite proposals: 850 or 1000 g. Which one is right?
 
The sight glass is accurate, as you are seeing the liquid refrigerant circulate thru the system. The cloudiness being refered to is tthe non liquid refritgerant. If you are going to do it by weight, good luck as + or- a few grams will make the difference between cool and cold.


Armando
 
xory72 said:
Scott,

When adding R-134 to your car ... the AC on full (MAX), blower on high, recirculating air etc. Look at the little glass "Eye" and it will most likely look cloudy / milky. Open the valve to add R-134 and when the eye clears up your system is full.

Hope this makes sense. I just did this with him on my NSX about three weeks ago! Super cold air now!

Good luck!

Darrin
Click to expand...

Thanks, Darrin, but I tried to just add R134a via the method above, and it seems that when there is no refrigerant in the system that I can't get any suction.

So, I'm guessing the system has to be evacuated and a vacuum put on it before it will start taking any of the refrigerant.

Does that sound right? Or am I not filling the refrigerant properly?
 
The refrigerant goes in under pressure not under vaccum. Make sure that if you are using the r134 cans that the piercing needle is doing its job. Also are you charging thru the suction side of the system? The cans have more pressure than the low pressure side of the system


Armando
 
MiamieNeSeX said:
The refrigerant goes in under pressure not under vaccum. Make sure that if you are using the r134 cans that the piercing needle is doing its job. Also are you charging thru the suction side of the system? The cans have more pressure than the low pressure side of the system


Armando
Click to expand...


Armando, as you're looking at it from the front of the car, I tried filling it off of the left most inlet, assuming that to be the "low" side. Is that not correct?

I always thought you filled off of the low side...

Thanks,
 
email me a picture as my memory recall is not working. I will circle the right valve. When you connect the gauges, what pressure do you have with the car running and the ac on high?



Armando
 
Hey guys the low side is on the left towards the firewall. The one behind the light on the right is the high side.

1. Make sure your valve has puntured the R134 can.
2. Connect to the low side Keep the valve closed.
3. Start the car ... A/C MAX, Blower high, Recirculationg Air etc.
4. Turn R-134 can upside down and then open valve. The can should get so cold that you can not hold it with you hands after few mins.
5. When can is empty, and if galss not clear, hook up a second can.
6. You should also see the little bubbles moving in your receiver.
7. Once this clears ... you have enough R134 in your system.

Now ... if you have moisture in your system (leaving a hose open for a length of time) ... you may have to "dry" buy removing the moiseture depending on your climate. However, I had a hose open in my car from when I bought it. I am sure is was open for possibly a year. I replaced eveything A/C related from the firewall forward. My buddy came over ... hooked up the R-134 to the low side, turn the can (larger can) upside down, opened the vlave and within a 20 seconds the receiver glass was cloudy and 2 minutes later it's cleared up.

I now have super cold air. The A/C actually got colder once the glass cleard. My A/C system was compeletly empty of R-134.

Hope this helps.

Darrin
 
Turn R-134 can upside down and then open valve
Click to expand...

Please No. Keep it up right...you want gas to go in, not liquid....compressors don't like to compress liquid. The nozzle will also freeze up causing delivery issues too.

You put the can in a bucket of water to keep it from freezing. You should wear safety glasses and some gloves.


R-134 runs at higher pressures than R-12, so you need to use about 10% less. R-134 runs with bubbles.

**

The only test that matters on an A/C system is the temperature and pressure. Monitor your pressure, ambient temperature and evaporator temperature. The book has a neat, but complicated looking, graph that will tell you when you've added the correct amount.

Over the years I've gotten so lazy that I pronounce success when I get the evap down to 40F and the pressures aren't out of whack. Too many people take advantage of my MVAC license...

Drew
 
Last edited:
That's the interesting part. My buddy owns his own A/C business (business/commercial) and refills his own vehicles (small cans) and large units by placing the tanks upside down. The can says right side up. Apparently..... I believe he said something about having the right about of each???? (gas/liquid)

Oh he also teaches A/C and refridgeration at the college, and certification course for messing with the refridgeration.
 
As the liquid leaves the high pressure refill tank to the lower pressure system, it flashes to vapor anyways (kinda like nitrous). It shouldn't make a difference whether the refill tank is inverted or not. At least in theory :wink:
 
I tried to use the can right-side up on a few occasions and it almost seems like it doesn't come out. So I get lazy and I turn it upside down.
Click to expand...

Get lazy by putting the can in a bucket of water (just regular hose water). It is done when it floats to the top....so you can do something else when it is filling.

It *should* boil into a gas before getting into the system, but the rewards are low for such behavior.
1. If you do suck liquid into the compressor: it will grenade.
2. The liquid is very very cold and you can damage fingers and eyes if you have a catastrophic failure causing the liquid to spew out.
3. If you do have a leak, the bucket of water will essentially make it harmless because water can dissipate/transfer a lot of heat.

While these scenarios are unlikely, it is a low reward high risk activity.

I wear safety glasses on just about everything now: I never want to go to the hospital AGAIN because I lodged shards into my eyes.

Drew
 
Unless you have a vacuum pump to draw negative pressure on the system and boil out the moisture, you are not servicing the system properly.

As with most Honda A/C systems, if you fill the system until there are no bubbles at all in the sight glass you have over filled it, and will shorten the life of the compressor and pressure switch as they will have to cycle on and off more often to deal with the excess R134A.
 
R14A [sic] costs less and works better.
Click to expand...

R12 has a transfer efficiency of about +10% over R134a. It also runs at lower pressures, which is easier on the compressor and system overall.

You can put R12 into a R-134 system for better cooling.

**

It is hard to determine closed system costs. R12 has been legislated out of existence because of its low initial cost and its extremely high cost to the environment.

So I'm in total agreement with you: Use R-134 as the actual performance difference is negligible and the environmental costs are much much lower than R12.

And yes, the system should be evacuated if it is completely discharged.

I have a pump if anybody wants to drive their NSX by for an evacuation...it is extremely heavy and unreasonable to ship.

Drew
 
zahntech said:
Unless you have a vacuum pump to draw negative pressure on the system and boil out the moisture, you are not servicing the system properly.

As with most Honda A/C systems, if you fill the system until there are no bubbles at all in the sight glass you have over filled it, and will shorten the life of the compressor and pressure switch as they will have to cycle on and off more often to deal with the excess R134A.
Click to expand...

+1

you need to remove all the left over first before putting in new oil and R134.

also when you put in the r134, you need to the a/c manifold gauges to view the system as you put in the r134 and make adjustments in how much r134 to put in based on the psi on the low and high reading or you risk under or over filling system.

you can try to put in a can or two and see what that does. if it works, great, if it does not, bring it to someone that knows what they are doing.

happy motoring

Rob :)
 
drew said:
I wear safety glasses on just about everything now: I never want to go to the hospital AGAIN because I lodged shards into my eyes.

Drew
Click to expand...

why didnt you blink? :wink:

j/k.

why did you open your a/c system white it was charged? :smile:
 
The reason I push the "go back with R12" is, NSX's are already cursed with weak links in the AC system lines and evaporator and all eventually have this problem down the line. When doing an AC repair wheather it be an evap. job, compressor replacement ect. You want to keep the pressure as low as possible to protect your system from further leaks. When you retrofit you will notice the orings are more beefy than the original. This is to withstand the added operating pressures from the 134. If you don't replace every oring in the system with the beefy ones, some of the original orings mostlikely will eventually fail. I learned this retrofitting cars years ago. The compressor shaft seal eventually lets go as well. Just my .02 looking out for ya.:smile:
 
My '92 was converted to 134 exactly 2 years ago. Every A/C component is original (knock on wood).

With the upcoming hot SC summer, I checked the pressure in my system. Using an el cheapo gauge, it was at ~37 psi and blew cool air (I guess as good as it's been from what I recall). I went ahead and charged it to 45 psi.

There are still bubbles in the sightglass which is OK per Zahntech. Don't know what it was charged to when it was converted? Does this 45 psi pressure sound OK?

Thanks,
Dave
 

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