AC systems designed for R12 - Page 2 - PeachParts Mercedes-Benz Forum

Diseasel300 · #16 05-15-2017, 10:25 AM

You need to make sure your temperature sensors are all in the right places. There is a "freeze stat" that cuts off the compressor when the evaporator temperature drops close to freezing to prevent ice and frost formation.

When your system is charged properly, you should be mid-high 30s at the center vent with the fan on low. Colder than that and you'll ice the evaporator up. This is an air conditioner, not a meat freezer, they operate on different principles and with different operating conditions.

Your friend's Honda only has pressure switches. If he's running that cold, you're probably off on charge. A lot. Hondas hold such small amounts of refrigerant that if you overcharge it by even an ounce you can expect to be buying him a new compressor sooner rather than later. They won't put up with it for long.

ps2cho · #17 05-15-2017, 02:04 PM

Quote:

Originally Posted by Hit Man X

I have been using the conversion factor of 0.56 for R12 to R152A conversions. The 300E is on it now as the evap leaks. I only shot in 20oz last I recall as it holds just over 2lbs of R12 (2.1?). It did low to mid 40s last summer. 300psi on the high side is way high on 152A, even if it is 100F outside. It should have pressures very similar to R12.

One of my E23s is also on it as I wanted to see how it performed on a fresh system. Same temps as the 300E, car is black on black.

I've replaced my condenser, expansion valve and drier previously, I wonder if you can get blockages in the evaporator? The only parts of my system that are original are the AC compressor, evaportor and lines. I have all 3 of those in boxes to replace, but removing the heater box is a huge endeavor and I keep putting it off!

I wonder if somehow air is still trapped in my system? I'm using a vacuum pump down to 29mmhg...is there any way to be sure?

lorainfurniture · #18 05-15-2017, 03:46 PM

Use a micron gauge to ensure a good vacuum. Then charge by weight only.

lsmalley · #19 05-15-2017, 08:11 PM

Ideally, yes, charging by weight is the proper way to do it, but I would say just start charging the system and go based on what the temp feels like. When it reaches a level of coolness that you are satisfied with take it for a drive and test it out. Then check your pressures and see what you have. Way I figure, you will hit the proper or ideal charge anyways if the system is operating properly because over charge, it will feel so-so, same as with an under charge. When I charged mine to get the temps that I'm at, that is the method I used. When I went back to check the pressures I was at roughly ideal pressures on low side and high side. This is the method I used yesterday when I helped my friend do his civic....we only put in maybe a full can plus or minus. His system wasn't holding vacuum so since the 152 is so cheap and readily available we charged it anyways until we got the hissing noise of a leak....he had about 4 hardened seals that we replaced and finally no more hissing after 4 separate partial charges.

Diseasel300 · #20 05-15-2017, 08:13 PM

"Beer-Can-Cold" is a great way to get floodback to the compressor and trash the bearings. There's a reason you charge by weight.

Mimzer · #21 05-15-2017, 08:40 PM

If R12a is supposed to be such good stuff, why has 134a been the standard for as long as it has?

Diseasel300 · #22 05-15-2017, 08:42 PM

Quote:

Originally Posted by Mimzer

If R12a is supposed to be such good stuff, why has 134a been the standard for as long as it has?

Because 134a is what's been forced down our throats after R12 was taken off the market. R152a is not marketed as a refrigerant, which is why it isn't as well known as R152a or R290a (propane). Keep your shirt on, R134a isn't long for this world either.

Hit Man X · #23 05-16-2017, 07:45 PM

Quote:

Originally Posted by Diseasel300

There's a reason you charge by weight.

This is exactly right.

You guys with near 30oz of 152A in your W124s are overcharged. My 2.9lb/1300kg systems take 26oz of the air duster. The W124 is a smaller system, 20oz fills me up fully and puts up great vent temps considering I have a soiled condenser still and evap.

I used to have the conversion factor for 134A, but my computer died last year. If I can find it, I will post it.

ps2cho · #24 06-19-2017, 09:58 PM

I wanted to bump this thread and say that the r152a handles higher ambient temperatures so much better than R134a.

It was 118F today, and it was pulling 55F on the freeway, when last year in the same ambient, r134a was around 60F, so an improvement.

At idle, it jumped to 80F very quickly, but I am convinced at this point I am overcharged with oil. Once I fix some other issues, I plan to flush the entire system and put fresh oil in and see whether the pressures go down.

lsmalley · #25 06-19-2017, 11:28 PM

Glad to hear it that you finally got the r152a running through the system properly.

lsmalley · #26 04-24-2018, 08:41 PM

I put the r152a in my system last year after ditching the r134. It's starting to warm up here in the Socal desert so I thought I'd just update that the r152 is still going strong. Pulling low 50's temp at vent idling ambient outside temp was ~100 (the outside temp reading is higher on the display because the car has been idling for a while in the same spot). When I take it out for some driving I'll get the temps again while rpms are up. I'm guessing I should still be pulling vent temps in the 30's....maybe even lower since its not 110*+ outside.

*UPDATED* Took car out on the Hwy today, 95* ambient temp and was pulling 30*F at the vent. It's been about a year now and considering we extreme heat as high as 120*, I'm calling this a permanent solution.

okyoureabeast · #27 04-25-2018, 03:19 PM

What oil is recommended for r152a?

lsmalley · #28 04-26-2018, 12:31 AM

I am running PAG oil 150. No issues for a year.
https://drive.google.com/file/d/1N0PZIJbXwYM8njGgZDFTvLhs_4iyjA_b/view?usp=drivesdk