I have a 1996 e150 XLT van. I've had it 30 years and have never touch the air conditioning system. The compressor and clutch work fine but it wasn't blowing as cold as it used to, so I want to add some 134a. Can someone tell me what's the maximum I can safely put in the system. I've heard between 30 and 40 but I would like a more specific number and also I'm getting mixed messages about whether to add any oil to the system. Since I've never done any tune-up or maintenance to it I was under the impression it would not hurt to add some oil but then I've been told unless it's broken not to put any in it could somebody please give me some information here thank you Teresa

 

Unless the system had a huge leak or part replacement,adding oil not usually required.

Suggest you read up a little on how air conditioning works before attempting adding refrigerant..
It is not difficult, but can hurt you if you do not know what to do and what not to do;..

 

I know to use low side, to watch my gauge so as to not overfill, to keep can upright but shake and turn between 12 and 3. What idk, and hope someone can tell me is what is capacity of my specific e150. I get a wide range of values and different measurements when I research it.

 

The capacity doesn't mean beans , unless you vacuum out the system and have a scale to weigh the amount you are installing.

If you suspect the system is low on refrigerant, you will hear the compressor cycling faster than usual.
What kind of gauges do you have to use ?