A/C Help -- Charge Question - Page 3 - PeachParts Mercedes-Benz Forum

leathermang · #31 06-22-2004, 07:23 AM

WHunter, I still can not figure out what you are intending to say...

The loss of system efficiency due to changing to the less efficient R134a molecule is widely accepted as about 15 to 20 percent. This is why I thought your 2 percent was a typo...that you meant 20 percent.

"Roughly 2% system fluid capacity loss."
Since you state you can pull 98 percent of the oil out of a system with your equipment.... is this 2 percent related to that statement? And perhaps stated backwards ?
98+2=100 ?

Since AC refrigerant is measured by weight... since it is only liquid under certain conditions in which seeing how much fluid is present is not usually possible I did not think you were referring to the refrigerant.

Your use of the term ' capacity' as compared to amount in the system made me think your original statement ( which it looks like you have edited out ) referred to cooling capacity of a system.

whunter · #32 06-22-2004, 06:42 PM

They have me on so many drugs to kill the pain, it is no surprise that I am not being clear.

Roughly 2% system OIL capacity loss is what I was trying to say.

The loss of system efficiency due to changing to the less efficient R134a molecule is widely accepted as about 15 to 20 percent.

In general; that is true, a very skilled climate control mechanic can achive only 13% loss.
This is not possible in a general shop environment, it takes too much time, effort and training.

FrankM · #33 06-22-2004, 06:59 PM

Using 134 I get 40° F vent temp on a 90+° day with high humidity.

My trick is to fill the system on the low side... plenty of bubbles in my dryer's viewer.

On a 126 two 12 oz cans seem to work well..

whunter · #34 06-23-2004, 04:32 PM

Hello Frank Mulone
RE: Using 134 I get 40° F vent temp on a 90+° day with high humidity.

What is your high side pressure running?

FrankM · #35 06-23-2004, 05:29 PM

Quote:

[i]
What is your high side pressure running? [/B]

I sold my gauges in 1996 .....

I have an R4 compressor. AUX fan is on. Compressor fairly quiet..

Many bubbles in sight glass...

jdblann · #36 06-23-2004, 06:26 PM

Abner,

Just wondering if you got it charged.
How did it turn out?

NC Benz · #37 06-07-2007, 03:27 PM

Why does R134a need the "green things"? What is the difference?

Quote:

Originally Posted by flash123

Whuh Oooh
Something is wrong here!

R12 is fine with the old fashioned "O" rings. R134 has to have those green thingies. Changing from R12 to 134 requires replacing the "O" rings, going back to R12 does not. R12 is fine with either type of "O" rings.

R12 is normally used with mineral oil. All the oil has to be removed and replaced with synthetic when changing to 134. The synthetic Ester does not mix with mineral oil.

I think the preasure is sopposed to be 25 lbs on the low side and 2.2 times the ambient temperature on the high side. You're going to have to look that up.

Pull a 29 inch mecury vaccum and hold it for five hours. If it does not hold, restart vacuum pump and pump back down and maintain for at least 2 hours. The system must bew able to sustain 29 inches without a pump for at least 2 hours. If not there is a leak or fluid left in the system boiling.

The A/C thermometer is about $5.00 at harbor freight.

Remember once you have converted to 134, you have a 134 system. It is not legal to convert a 134 system to R12.

The tag that came with my compressor said 6 to 8 ounces of oil. Another source said 6.8 ounces. Take a two ounce syringe and add 2 ounces to the compressor. Then put the rest in the evaporator, drier, condensor, and hoses. Some sources say 2 ounces in the condenser, some say spread the rest around equally. So 2 ounces in the compressor, 2 ounces in the condenser, an ounce in the dryer, an ounce in the evaporator at the expansion valve, and an ounce in the hoses should be OK.

Always wet the "O" rings with the oil you are going to use before installing.

bobtasco · #38 01-29-2008, 09:10 PM

on a related note, This is a sort of incredibly dumb question but I'll shoot. Its a 300D Turbo. 1982. I am trying to recharge is retrofitted with the 134a system. It just needs a new charge. The bottle on the back reads do not plug into top end service valve. It may explode the can. Duly noted. I plug it in the only valve I see with the 134a fitting (this is the valve slightly towards the windshield of the radiator, topside near the valve cover) and try to connect it and tap the can, but no go. There is no pressure from the can to the AC unit. I am reading the pressure gauge on the can that comes with the 134a recharge hose. No pressure. Hmm. Spider sense is going off. What do you guys make of this?

Matt L · #39 01-29-2008, 09:18 PM

The high-side fitting is hiding below. I think it's on the right side, deep in the guts of the engine. The low-side is on top, where you were connecting. If the fittings are installed correctly, you can't connect to the wrong one as they are different sizes.

I don't quite understand "no pressure from the can to the AC unit." Can you elaborate? You should see something when releasing refrigerant from the can.

sailor15015 · #40 01-29-2008, 09:18 PM

Is this one of those cans with the throw-away dispensing valve included? Are you sure you read all the directions and have popped any tab or anything that may be required to release the contents? Does the car have the proper snap-on r134a fittings, not the r12 threads?