I've known some do-it-yourselfers who have done that and gotten away with it, but no professional would try to charge the system without pumping it into a vacuum first. The secret is to get the new compressor hooked up as quickly as possible. Don't pull the hoses off, then quit for the night and finish the job the next day. The goal is to get no air in the system because of the humidity in it.
Pumping the system into a vacuum makes any water vaporize at 77 degrees so it can be drawn out. The system works by flowing the refrigerant through a very tiny orifice. That's where the pressure goes down, the refrigerant expands, and gets real cold. If a little water is circulating, it will freeze at that orifice and stop the flow of refrigerant. It can take ten to thirty minutes for that ice to melt and the system to start cooling again. Also, water and refrigerant mix to form an acid that corrodes metal parts.
I suspect you're going to use the do-it-yourself bottles of refrigerant to charge the system. Refrigerant is very dangerous to work with. It can cause blindness and frostbite. Most professionals wear gloves, safety glasses, and a face shield. Be aware too that cars can handle more over-charge than a home refrigerator, but too much refrigerant in the system can let liquid slosh into the compressor. At the least that will lock it up. At the worst it can damage it. Chrysler is the only manufacturer that uses a sight glass that will show when the system is fully-charged by the absence of vapor bubbles. Ford started using sight glasses too, but there will still be bubbles when the system is fully-charged, so they don't do much good. As with all other car brands, you have to go by the size of the cans and get as close as possible to the amount listed on the sticker under the hood.
When you start with a vacuum, that makes drawing in the refrigerant faster because a lot will go in before you reach 0 psi. Without a vacuum you will likely find you can't get enough to go in on its own. It will help to place the can upright in a pot of hot water.
Saturday, July 5th, 2014 AT 2:35 AM