A/C pressures and volumes - Freeze 12.. - PeachParts Mercedes-Benz Forum

baudenfj · #1 05-23-2010, 11:43 PM

Hi Forum:

I have a 300 SD - 83.. I put in a new compressor, expansion valve.. flushed the A/C lines and plan to refill with freeze 12..

I already have about 700 gr of freeze 12 in the system. It works but I need to top it up and don't seem to be able to find the pressures (high/low side) for R12/Freeze 12.

The system cools reasonable well and plan to increase the amount of freeze 12. Could anybody let me know what pressure I should charge the system to... Currently I have 15 bar on the high pressure side and 2.5 on the low side.

I have the chart for a 124 for R134 and it shows the high pressure should be about 20 bars for the temperature I was evaluating the system (32 deg C.)

How much freeze 12 should I add....

Thanks for your help...

Cheers ....

vstech · #2 05-23-2010, 11:51 PM

... have you changed the oil in your system to PAG? or Ester? you don't want to use mineral oil with Freeze 12 which is a mix of 134 and 114, I think, anyway, it's not R12.
pressures are not absolute, they depend on the ambient and vehicle interior temps, and airflow.
in TN, I'd want true R12 in the system, if I just spent all the money you have with your system.

soothappens · #3 05-24-2010, 12:16 AM

On the 300SD it shows 3.2 LBS of R-12 on my sticker. You go on Johnson's freeze 12 site it shows 43 oz. as the conversion. As vstech said use the ester oil it recomends this on the site as well . Not in such a clear wording but it tells you that due to loss of oil from the change over you should replace it with ester oil. Buyer beware.

Drop in replacement...80% R134

!!!

Graplr · #4 05-24-2010, 10:17 AM

Quote:

Originally Posted by soothappens

On the 300SD it shows 3.2 LBS of R-12 on my sticker. You go on Johnson's freeze 12 site it shows 43 oz. as the conversion. As vstech said use the ester oil it recomends this on the site as well . Not in such a clear wording but it tells you that due to loss of oil from the change over you should replace it with ester oil. Buyer beware.

Drop in replacement...80% R134

!!!

Are you sure about that? It has been awhile since I looked at mine but I believe it is 2.9 lbs and that the 123 300Ds were 2.6 lbs.

It is best to slightly underfill the system than overfill it.

baudenfj · #5 05-24-2010, 10:57 AM

Yes, the system is labeled and Yes, I changed the oil to ester oil.

Since I am doing all the maintenance myself I did not want to deal with R12. I thought I try freeze 12.

I have about less than 2.0 lb in the system.

On my label it say I should put 1.0 kg R12 in! However, I think the label is not correct and I read that the SD requires more! I think 2.9 lb sounds right but I would like somebody to confirm it!

I can do the freeze 12 R12 conversion.

Is there a way I could charge it by pressure rather than by weight. I know I need the diagrams and the pressure depends on temp, humidity, air flow (full fan speed).

Cheers...

alabbasi · #6 05-24-2010, 01:09 AM

I think that it's 40 on the low side and 250 on the high. Pressure should be the same volume would be different.

#7 05-24-2010, 09:09 AM

Tsk, tsk, tsk......

I assume that you used the correct Freeze 12 fittings and properly labeled the system as required by Federal law! If you did not, you are setting up a disaster for some poor guy in the future who will unknowingly recover the junk into his R12 tank which will contaminate the entire tank incurring the loss of all refrigerant in the tank, plus incurring a disposal fee. PLEASE use proper fittings and labels to prevent this disaster for some innocent tech. That poor guys is just trying to put food on the table and shoes on the baby like everybody else.

vstech · #8 05-24-2010, 11:10 AM

not accurately, weight is the way to put in freon.
the reciever needs to hold the correct volume of liquid for the system to work in all climates, charging by pressure/temp can be done, but it requires several contact thermometers and proper pressure slide charts... I'm guessing the freeze 12 kit did not come with bubble/pressure charts?

#9 05-24-2010, 11:46 AM

^^^^^^^^^^^^^^^^^^^^ Listen to the man!

Probably the most handy piece of a/c service equipment I've bought beyond gauges and my recovery machines has been my charging scale. Got it for $80 off of ebay. Most useful $80 piece of equipment I ever bought.

Graplr · #10 05-24-2010, 12:10 PM

Quote:

Originally Posted by LarryBible

^^^^^^^^^^^^^^^^^^^^ Listen to the man!

Probably the most handy piece of a/c service equipment I've bought beyond gauges and my recovery machines has been my charging scale. Got it for $80 off of ebay. Most useful $80 piece of equipment I ever bought.

I love my charging machine. I got a smokin deal from a fleet maitenance company that was selling their R12 stuff off on Craigslist. For $100 I got a reclaim machine with about 10-15 pounds of reclaimed R12, a charging machine with a 30lb keg of R12 with about 3lbs left in it. The office guy put it up for $100. I went to buy it and he said the techs told him it was worth more and he relisted it for like $300. He sold it to me for $100 since we had the deal already worked out. I was grinning.

Matt L · #11 05-24-2010, 09:01 PM

Quote:

Originally Posted by LarryBible

^^^^^^^^^^^^^^^^^^^^ Listen to the man!

Probably the most handy piece of a/c service equipment I've bought beyond gauges and my recovery machines has been my charging scale. Got it for $80 off of ebay. Most useful $80 piece of equipment I ever bought.

A heated charging cylinder is also nice. I use a scale to check the fill of the charging scale, since it's easier than using pressure (temperature) and level.

But I also use the scale for non-AC work. For example, to suck some transmission fluid out of a car and replace it with new. I weigh the extractor before and after, and know exactly how much came out.

vstech · #12 05-24-2010, 09:04 PM

Quote:

Originally Posted by Matt L

A heated charging cylinder is also nice. I use a scale to check the fill of the charging scale, since it's easier than using pressure (temperature) and level.

But I also use the scale for non-AC work. For example, to suck some transmission fluid out of a car and replace it with new. I weigh the extractor before and after, and know exactly how much came out.

you do WHAT with a heated charging cylinder????
wow, I'd kill anybody that used my HCC for anything but refrigerant!!!

you ever seen a canister mity-vac? that's what it's used for, fluid extraction... wow, just wow...

#13 05-25-2010, 09:04 AM

Quote:

Originally Posted by Matt L

A heated charging cylinder is also nice. I use a scale to check the fill of the charging scale, since it's easier than using pressure (temperature) and level.

But I also use the scale for non-AC work. For example, to suck some transmission fluid out of a car and replace it with new. I weigh the extractor before and after, and know exactly how much came out.

Yes a heating blanket is particular nice for a commercial shop where time is money. That's one of the "like to have" items on my list, but a refrigerant identifier and sealant detector are above it on the list.

vstech · #14 05-24-2010, 12:10 PM

OK, I've made it on the forum! I've been called "the man" by LarryBible!!!!

layback40 · #15 05-24-2010, 12:21 PM

Congratulations John!!! The man !!!