'81 300SD Where do I add freon? - PeachParts Mercedes-Benz Forum

tyl604 · #1 05-19-2015, 01:10 PM

Which fitting to you use to add Freon? And do you hold the can upright or upside down? How do you identify the correct fitting? It has been a long time and I do not quite remember. Maybe someone can post a pic.

Zulfiqar · #2 05-19-2015, 01:14 PM

you add from the suction side, its the fatter of the two pipes. Only charge in vapor - can upright.

before you add - make sure you have the correct type of refrigerant and you have an idea what you are doing.

BayouFlyFisher · #3 05-19-2015, 01:16 PM

Quote:

Originally Posted by tyl604

Which fitting to you use to add Freon? And do you hold the can upright or upside down? How do you identify the correct fitting? It has been a long time and I do not quite remember. Maybe someone can post a pic.

Go to Youtube and watch some videos. Good luck

tyl604 · #4 05-19-2015, 01:22 PM

Thanks. I know what I am doing; in fact I installed the new AC myself a few years ago. However the freon (R12) is low and I have some. Just did not remember where and how to put it in. My only problem is that I do not have gauges. Suspect I can just watch the bubbles and stop when they disappear.

Did not think about utube. Will check it out.

Thanks for the info.

leathermang · #5 05-19-2015, 02:03 PM

You do not realize how much you do not know what you are doing...
FIRST off... the FSM warns against using the site gauge to determine your refrigerant level.
You risk OVER filling using it.....
You need gauges to do this correctly... maybe you can borrow some...

tyl604 · #6 05-19-2015, 02:17 PM

Yes; I am sure you are right. I see that it takes 54 oz and the low pressure is the larger pipe. My indy in Atlanta actually does not work on R12 any more or I would take it to him. And there was a forum member in a suburb of Atlanta who had hoses about 4-5 years ago. We filled it up to max allowed pressure and it still had some bubbles.

Not much on utube. Really out of date with R12.

leathermang · #7 05-19-2015, 02:19 PM

Tell us more about your leak and how you fixed it...

This stuff can be dangerous....
forty years ago.... I hooked up to the wrong side.... and luckily felt of the R12 can.. it was hot... it should have been cool....
Always wear goggles no matter how sure you are of what you are doing...
frozen eyeballs can happen in an Instant....

tyl604 · #8 05-19-2015, 02:24 PM

Did not fix a leak. We put in some R12 to max pressure but it still did not cool properly as I remember; was 4-5 years ago. Cooled some but as I remember did not work perfectly. It stopped cooling completely last summer or the summer before and I saw bubbles in the site glass. Have done nothing since and am contemplating putting just a can of R12 to see if it works.

Have three cans on the shelf. That said not sure it will cool at all any more. Do they still sell the leak detection stuff?

leathermang · #9 05-19-2015, 02:32 PM

Do not suggest the leak detection stuff.....
a chance it will cause other problems ... particularly at the txvalve....
just find sniffer which will detect your refrigerant leaking..
if you overfilled it....
that will cause it to not work great..
and overwork everything in the system....
it will work great with several oz less than full...
works way too hard with even ONE oz overfill....
find sniffer best bet right now...
or borrow one..

You just have to get some gauges .... you may not have any in your system...
so you would not want to waste a can when that by itself will not even activate the low pressure switch....

tyl604 · #10 05-19-2015, 02:42 PM

Sounds right. Thanks for the help. Will give it some thought. I guess I could just vent say 2-3 seconds in the air; maybe a bit more. If nothing happens, I will know that there is zero R12 in the system. If something does zip out and it is actually slightly overfilled, maybe that would be enough release to make it produce some cooling again. Had not known that too much freon could zero out cooling potential.

Uh oh; wife calling. Done for now.

leathermang · #11 05-19-2015, 02:45 PM

Differential pressure change is the entire ballgame on AC...

Cars use different amounts of refrigerant... look for the info on the car.. or in some manual for your specific car....
So when you quoted that 54 oz.... you were not weighing that...
but using the site gauge to say ' full ' ?
it must be weighed to be correct....
or use the gauges... but they are dependent on correct set up of the ' test' condition..
and most of us do not have a good enough fan to force air through the condensor... for perfect test.... and temperatures are taken with pencil thermometer AT the center Vent..
with the blower on LOW.....and the windows OPEN..... that will be news to a lot of people......LOL

ah-kay · #12 05-19-2015, 03:18 PM

Quote:

Originally Posted by leathermang

Differential pressure change is the entire ballgame on AC...

Cars use different amounts of refrigerant... look for the info on the car.. or in some manual for your specific car....
So when you quoted that 54 oz.... you were not weighing that...
but using the site gauge to say ' full ' ?
it must be weighed to be correct....
or use the gauges... but they are dependent on correct set up of the ' test' condition..
and most of us do not have a good enough fan to force air through the condensor... for perfect test.... and temperatures are taken with pencil thermometer AT the center Vent..
with the blower on LOW.....and the windows OPEN..... that will be news to a lot of people......LOL

I think we need a 'Rocket scientist' to fix our A/C if the above is true. It means when you pay $1k to book it into a A/C shop to have it repair is a BARGAIN. It means every test has to be perfect and all the tools need to be calibrated.

In reality, you can do your A/C without too much money, too many test tools and not in perfect environment.

leathermang · #13 05-19-2015, 04:04 PM

Quote:

Originally Posted by ah-kay

I think we need a 'Rocket scientist' to fix our A/C if the above is true. It means when you pay $1k to book it into a A/C shop to have it repair is a BARGAIN. It means every test has to be perfect and all the tools need to be calibrated.

In reality, you can do your A/C without too much money, too many test tools and not in perfect environment.

Man, I am glad you have finally come around to my way of thinking....

JessieAMorris · #14 05-19-2015, 04:18 PM

See if you can find some gauges. A lot of pawn shops have gauges for ~$50, but you will need R12 ones.

With the gauges you can see if it's still got a charge, if the compressor is working, if the fan is working, etc. You really do need gauges to get a complete and total view into your AC system.

If you still just want to eyeball it, is your compressor seized? Does the clutch engage? If not, if you close the contacts on the low pressure port on the receiver drier does the clutch engage (only do this for a second or so tops, no refrigerant means less oil to lubricate the compressor)? If it does engage, you likely do have a leak. If that's the case, you need to first find and fix the leak, then replace the receiver drier (somewhat optional, but highly suggested), and then vacuum down the system and finally recharge it.

It's a somewhat large job, but it's doable.

leathermang · #15 05-19-2015, 04:32 PM

Jessie, Where do you get the idea it is ' somewhat optional ' ?
All the MB FSM instructions call it mandatory... all the industry standard advice requires it for any warranty they may offer....
The cost of the receiver dryer .... compared to the cost of any moisture making acid and causing flaking inside the metal parts of the system..... does not make it a good money bet to leave it off....
You should study the threads already on the forum...like the one in my signature..... and remember , we have moderator Vstech and his experience as a professional HVAC person.... introducing opinion where physics is at work makes for short AC lifespan and a lot more work and money expended....

AND we suggest using Nitrogen or argon or something to TEST the system in its working condition.. under pressure... so the load on gaskets and joints has a better possibility than ONLY using vacuum and risking expensive refrigerant loss when having to go back and fix a leak missed the first time...