Be sure that you aren't making things worse before you start by knowing what must be done.
First rule, introduce nothing but 134a unless you also need to add PAG oil. If you don't know that you need oil, you probably don't. A fast discharge will cause oil loss, whereas a very slow leak will usually not. Adding a very small quantity of oil containing dye is acceptable for systems not already containing dye.
A corollary of the first rule is to never use something that is advertised as containing a sealer or o-ring conditioner. You don't need these and they can cause harm, sometimes resulting in a total system replacement.
Another not-so-obvious corollary is to properly purge the hoses of your fill equipment. You do not want to inject even a small quantity of air into the system.
Second rule, ensure that you actually need refrigerant before adding any. You can make a good guess by measuring the pressures and looking at the chart. A gauge on the high side is required for this, ESPECIALLY on a '96. There is a TSB for a defective (plugged) dryer for the very early cars. If yours is plugged, the reading at #7 will be far lower than the actual pressure at the compressor. On point, my '96 read 3 at the #7 reading but had 350 PSI actual high-side pressure.
1996 E320 A/C Recharge? 
Linear Mode
