I was looking at some kits on eBay for adding some R-12 to my system. It definitely needs a charge because now that it's hot, the air isn't blowing cold anymore.

There are various kits on eBay that sell 12-oz R-12 cans along with a can of oil for R-12 systems. They include the can tap with a hose that ends with a schroeder valve. Some kits also have a pressure gauge.

A few questions:

1) how much of that oil should I put into the system?
2) some kits sell a pressure gauge inline with the filling hose. which pressure readings am i looking for to know that the system has enough R-12 added?
3) the instructions say to use a low-side port for filling. i've been told that on the 300SD, the low-side port is located up front behind the grille next to the radiator... can someone verify that please? there's another port that's by the firewall - is that the high-side service port?

yes, they do sell r-12 on ebay but you must send them a copy of your
hvac lisences. So you have done all that.
Yes, there is an online lisence system.


If you have not then look into freeze 12. or Ev 12. These do not require the
lisence. dieselgiant has the freeze 12... it works well.

I do have the license for buying R-12 and I'd like to stick to it for now.

Deniss, I do not understand how you could have a license and still have such basic questions about AC... I suspect you have ' access' to someone with a license who will help you buy it .... (?)
You need to go to aircondition.com and read their ' knowledge base' section.
Your basic assumption about the hot air and low R-12 is faulty. There are all sorts of other things which can cause that symptom... but even if it is low you need to address WHY it got low before dealing with the charging side of the equation...

No, I *do* have an EPA Section 609 cert from MACS - not using someone else's license. Have you taken their certification test? If you did, you would know that it doesn't really teach you much about the actual service, just outlines some safety and environmental concerns and outlines some basics about refrigerant recovery and recycling. It doesn't teach you to be an AC tech.

Now, moving past my license/certification and my lack of knowledge in the field of automotive air conditioning...

What can be some of the things that might cause the AC system to not produce cool air, other than the lack of refrigerant?

Aircondition.com is used as a reference by all sorts of persons including professionals...
If you had run over and scoped it out you would realise they have already presented the answers to your question way better than anyone on this site can.

The Aircondition.com 'knowledge base' section can't be beat...

You must stick guages on both sides of the system and stick a thermometer into the center vent and turn on the system for at least ten minutes outside but not in the sunshine to establish anything in terms of a base line to start from.

Hey,
Your question #1 is the key to your answer. There is no way to know how much oil to add because you have no way of knowing how much oil is left in the system.
I don't think I need to tell you what the lack of oil will do to your compressor and adding too much oil is just as bad.

The proper way to fix it would be to find the leak, fix it, flush the system, pull a vacuum and recharge with the proper amount of oil and refrigerant.

What you can do is put some R-12 in and look for the leak. When the charge gets low again that it doesn't work then you can go on to making the proper repairs.

Danny

__________________
1984 300SD Turbo Diesel 150,000 miles

OBK member #23

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination