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How many 12oz cans of R134a in a 73 RV2 system?

YY1

YY1

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Continuing my pressure switch replacement thread here.

Vacuum held overnight.

I was advised (by the parts store) 3.5 cans.

3 cans had 20 pounds (psi?) on the low side and just over 200 on the high side.
Blowing just under 50 degrees.

Added that 4th can and 22# low side 210# high side.
Blowing 45 degrees.

How come refrigerant is sold in 12 oz cans but spec'd in pounds?

IIRC FSM says 50 low side 225 high at 90 degrees ambient temp.

For reference my 2015 Renegade blew 48 degrees on max recirc on the way home from the shop.

Am I good to go?
 
YY1 said:
How come refrigerant is sold in 12 oz cans but spec'd in pounds?
Click to expand...
The same azz clown marketing guru's that put different numbers of hot dogs and buns.
 
3.5 cans would be 2 LBS 10 OZS. That seems a bit much to me. The system should hold about 2.2 LBS. Be sure to add oil before charging. Your compressor should cycle from 180-190 down to 75-85 at 1000RPM. If it cycles too fast, your low on refrigerant.
 
I generally charge my vehicles a/c @1200 rpm, with r134a. suction pressure would be stable, no more than 35# (40 degrees), and not below 28# (about 33 degrees), i dont care about head pressure, as it will be high, as the vehicle is sitting still. vehicle physically moving, more air across condenser = lower head pressure. (in the range of 120#, depending on ambient, speed, condenser condition).
r12 would be slightly higher
 
Low side line icy cold and sweating your real close to correct charge.
No sweat and cool line your low
Frost and ice on that line your over.
When adding freon let it run long enough to work through the system and convert.
 
metaldad said:
I generally charge my vehicles a/c @1200 rpm, with r134a. suction pressure would be stable, no more than 35# (40 degrees), and not below 28# (about 33 degrees), i dont care about head pressure, as it will be high, as the vehicle is sitting still. vehicle physically moving, more air across condenser = lower head pressure. (in the range of 120#, depending on ambient, speed, condenser condition).
r12 would be slightly higher
Click to expand...

EXCELLENT explanation and advice.....R134A reacts differently than R12 use to....especially pressures. Because R134A has different specific heat characteristics, it can absorb more heat at a slightly higher pressure, like the 35# to 28# range noted. The discharge or high side pressure is a function of ambient air temps, it would be my advice to direct air from a box fan directed at the car's a/c condenser while charging, as it lowers the head pressures. Allowing the suction pressure to go lower than 28# will result in icing the evaporator coil and an overall lowering of sir flow. Just my opinion of course.
BOB RENTON
 
I totally forgot to switch the function off of "Max".
I'll have to try that next time to see if it short cycles.

45 degrees output, though.
No frost on any of the lines.
Did drive down the 50 MPH road a few miles and back.
Seemed to hold output.

Probably wasn't 90 degrees ambient because of cloud cover.

That 22 low side seems low to me.
I agree the 4 12 oz cans seems high as well.
 
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Does your dryer have a sight glass? If so add freon till you get a small bubble every couple of seconds. I've been doing that for years on systems with unknown capacity. A properly charged system should blow 40-45 degrees on high fan.
 
Systems back then generally held around 3lbs of refrigerant. When switching refrigerant to R134a, you should only fill system to 80-85% capacity. Sight glass will not be accurate when changing refrigerants, so you really need to know proper capacity charge and do the math. Or wing it and shoot for 40lbs low side (@80degrees, normal humidity, idle speed) and if it's cold, (anything at or under 40 degrees) you're done.
 
Is there a fluid oz to pound conversion involved?

If not- 12oz x 4 = 48, divided by 16 = 3 pounds.

I've also read that the oil stays in the system and doesn't get vacuumed out.
 
YY1 said:
Is there a fluid oz to pound conversion involved?

If not- 12oz x 4 = 48, divided by 16 = 3 pounds.

I've also read that the oil stays in the system and doesn't get vacuumed out.
Click to expand...

When switching or changing to R-134A refrigerant, you must change to the compatible oil. The correct oil to use is: new oil: Polyalkylene Glycol—or PAG oil. Note that there is another kind of oil called Polyol Ester Oil (POE). The advantage of ester oil is that it works with both R12 as well as R134a, so you can fill the system with it and then use either refrigerant.
Bear in mind that a large percentage of oil is retained in dessicant inside the dryer, as well as the compressor's crankcase and bottom of the condenser core. Straight R12 oil is not compatible with R134A refrigerant. In addition, for the long run, sealing O-ring should be changed as well as the hoses. The R-134A will diffuse thru the hose's inner liners and O-rings. Just thought you might like to know....
BOB RENTON
 
I didn't convert it.

It was "professionally" converted by the second owner before I bought it.
It's been running 134 since before 2012.

When I got it, it was low, but a vacuum and charge from my professional mechanic friend lasted about 6 years.
I've added a can twice since then until it vented on me this spring.

As mentioned above, I checked for green O rings where I replaced the dryer and found 1 of the 2 was still black.
 
B, E and C bodies held 54 oz of r-12. The common thought is 70 to 80%. (37 to 43 oz). Low 40s is pretty good for a conversion with original style condenser, mult-flo will be more efficient. Never charge a r12 conversion till the site glass is clear it is overcharged at that point always use gauge. The conventional thought is high side should be 2 to 2.5 ambient near the car. So 90° it is 180 to 225 depends on humidity and system efficiency ( these are inefficient for 134 so I lean towards higher.) alway vacuum the system for at least 30 minutes to make sure it is dry.
Also if the epr valve is still present it will never get cold since they are calibrated for r12 and stop it from going below 33psi at compressor... I know this from experience I didn't check to see if it had one drove me nuts.
 
72sunroof said:
B, E and C bodies held 54 oz of r-12. The common thought is 70 to 80%. (37 to 43 oz). Low 40s is pretty good for a conversion with original style condenser, mult-flo will be more efficient. Never charge a r12 conversion till the site glass is clear it is overcharged at that point always use gauge. The conventional thought is high side should be 2 to 2.5 ambient near the car. So 90° it is 180 to 225 depends on humidity and system efficiency ( these are inefficient for 134 so I lean towards higher.) alway vacuum the system for at least 30 minutes to make sure it is dry.
Also if the epr valve is still present it will never get cold since they are calibrated for r12 and stop it from going below 33psi at compressor... I know this from experience I didn't check to see if it had one drove me nuts.
Click to expand...
IMO....The FSM shows the charging procedures for R12 refrigerant. I believe it says: Charge to clear sight glass then add an additional 1/4# of R12. I also believe that also notes to use a box fan and direct the air flow across the condenser to keep discharge pressures lower. When changing over to R134A, less volume of R134A is required because it has a different specific heat characteristics and boiling point temperatures than R12, hence less refrigerant is required. YES...the EPR valve (located in the suction port of the compressor) MUST be removed as it is calibrated for different pressures. In addition, the TXV (Thermostatic eXpansion Valve) may need to be replaced because od the differences between the two gases. Personally, I never use the discharge pressure connection....I use only the suction pressures and the discharge air temperatures as the determining factor. Just my opinion of course.
BOB RENTON
 
on this same subject, I'm getting ready to change over my 72 Plymouth Satellite over from R-12 to R-134A. Where's the best place to get the complete gasket/oring kit to seal all breaks that I have to make in the system to flush it out properly ? I know of o-rings but I think there's some soft metal crush gaskets in some areas, am I right in thinking that ? Thanks for the help
 
cornpicker said:
on this same subject, I'm getting ready to change over my 72 Plymouth Satellite over from R-12 to R-134A. Where's the best place to get the complete gasket/oring kit to seal all breaks that I have to make in the system to flush it out properly ? I know of o-rings but I think there's some soft metal crush gaskets in some areas, am I right in thinking that ? Thanks for the help
Click to expand...
Classic auto air.
https://www.originalair.com/1961-76-mopar-rv2-compressor-manifold-gasket-set
The rv2 uses an o ring and a gasket in the back not the flat ones with the fingers sold at NAPA. The o-rings can just be the assortment pack, buy green ones.
In retrospect I would have never converted my system to r134, I have my ac certificate and can by 12, the hassle of trying to get the correct amount in ridiculous and I have a r134 recovery machine. I get low 40s in Florida summer r12 I got 30s.
 
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