I believe my 1994 850 need an AC charge. I had it charged 2 years ago, and after the charge it was very cold. Anyway, I'm trying to save some money so I thought I might try to charge it myself. Watched an interesting how-to video and it seems pretty straight forward. The only thing I didn't catch was what the pressure should be reading. This is the video I saw:


I have a few questions:

1. Should I turn on the "recycle" when running the AC for checking the pressure?
2. Do I leave it on that setting while adding coolant?
3. He shows the gauge reading as 20 PSI when the compressor kicks in, is that the normal reading?
4. What should the pressure show when it is fully charged?
5. Do I rock the can back and forth just before I start, or while I'm adding coolant?

Thanks in advance!

Alfredo

 

On a gauge like that it should be in the green. Closer to the red the better.

Then there is a table that takes temperature into account.
You only need to be concerned with the low side pressure.


When charging, turn the ac on, coldest temp, highest blower. Recirculate ... doesn't matter it it's on or off.

It doesn't matter what pressure you get when the compressors clutch is "off" or disengaged and the high and low sides will equalize and it's not uncommon to read well over 80psi ... do not let any out
You only care what the gauge reads when you know the compressor is running.

"Do I rock the can back and forth just before I start, or while I'm adding coolant?"
If it's something to do with a condition you have you can rock the can all you want but it's not going to make any difference in charging the AC.
You can "feel" how much is left by shaking it gently but you don't gain anything by shaking it like paint. You can hold it with both hands and the heat from your hands will push the freon in a little faster. A trick used to be to put it in your arm pit as the heat will vaporize the freon quicker and push it in faster but I NEVER recommend it because if you somehow manage to jam the connector onto the "HIGH" side the can will explode. It was easy to goof with the old R-12 connectors if you didn't know what you were doing. The R-134 connectors it's (almost) impossible.