Is it sfe to add enviro-safe to my existing freon?

has the freon leaked out -will need to repair leak add a tap-a-line valve then evac unit then using a set of gauges and correct freon add freon

buy can with hose adapter and hook it up according to instructions to the low side port the following link shows how to add freon to different vehicles your vehicle is not their but the explanation and how to are the same for adding freon
How To Add Freon To Auto Yahoo Video Search Results

There are simple conversion kits that basically just replace the service ports to use the r-134 type hoses, but it is best to have a pro evacuate system and flush it, draw a vacuum, add correct oil and freon. If the system has been empty or dead a while, best to replace dryer and orifice tube or expansion valve as well.

It is against the law to release any freon into the enviroment it should be done by a shop where they hook up a machine that sucks the freon into a sealed container for disposal.

Adding freon to a car requires connecting the low-side service valve first, followed by the high side, recovering the existing freon, evacuating the system of air and recharging the system with new freon.
You can use R-134a refrigerant for 1998 Ford Explorer. You can get all parts necessary for Ford Explorer at one place at http://www.carpartswarehouse.com/carparts/Ford/A-C_Condenser.html

If you have to ask that question, you don't have the equipment, (gauges, etc) to be able to safely recharge your AC circuit in your 1993 Buick Regal!

Sorry to be blunt, but you could cause more problems than you would fix if you try to do it yourself.
Do you know what freon is in the system now? You have to recharge with the same type and since you have an older car you probably have old type in it, which means you have to evacuate the system and capture the freon (and dispose of it) and then recharge with the right amount of new type freon.

Hi DO NOT BYPASS the tryrister switch!!!!!!!!!.

You can safely add R12 (freon) from a can with the system not running ,when you have enough gas and oil mix added to the system the compressor will stsart automatically the problem you have is not knowing if there is a leak in the system,as you need to check this as venting R12 to the atmosphere can land you in prison if caught !!!!,.The best advice I can give you is take the car to an Air-con specialist and he will carry out all the checks on the system for you and re-gas the system properly.

If you are jumpering the a/c cycling switch to kick the compressor on, you are likely low on freon. Get a a/c kit with a gauge on it to add a can of freon. Add about half a can and see if it starts cycling on and off. And, make sure the gauge reads in the "good" range. Then add some more. Make sure it does no go outside safe range.
When full, it should cycle on and off 4 to 7 times/minute at 70 degrees F.
You may have a slight leak.

report progress.

What do you mean by went out,if it just one day stopped working,it could just be low on freon.does the a/c compressor come on? to find out....start engine..turn a/c completely off....turn on a/c....as soon as you turn on a/c you should hear a click sound under the hood,if you dont hear click,you may just be a little low on freon.you can add freon yourself instead of paying alot at a shop.buy some r134 refrigerant,walmart sells several differnt brands just make sure it comes with a hose to add with.find your a/c low pressure line on car.....connect hose attached to refrigerant bottle...snap onto fitting on low pressure on a/c line.....start car with ac on add refrigerant......soon you should here a click....if so that was the compressor coming on,add freon until guage on bottle is in the safe zone. Ihopoe this helps you,if it doesnt you may need to take it to a shop.

Before you add Freon, you should check the leaking first, if the Freon is too low, sometimes cause this kind problems. use color Freon test it and tight the leaking area and then add Freon, you can not do it yourself because the law say.