R12 to new stuff

I don't post much but could use alittle help. I'm changing over my freon system and have the connectors fitted, but the valves won't open! any ideas? I'm changing it now because it needs servicing' but am always reluctant to force something I'm not familiar with. Thanks for any help. (1990 pioneer 4.0l):sunshine:

The valves are open now, you close them about 1/2 way to charge the system. Don't close them with the compressor running. Closing them is only to change hoses or something like that.

On my '85 you turn the valve CLOCKWISE about one and 1/2 turns (no more) to open the port for charging. I think this is what langer1 is saying but just wanted to emphasize the clockwise turning, as this has always seemed counter intuitive to me for opening a port. The ends of my valve stems are chewed up and I have to use vise grips to accomplish this.

The stem should turn easily after it initially breaks loose and you should be able to turn it with fingers or with a pair of pliers or an end wrench to lightly open and close during the charging process and then just snug it up when finished.

Thanks alot, for responding. Actually we've got an auto mechanic that is building helicopters for us now, very convienant. He's talked me out of the retro fit, seems it's not as simple as some would have you believe. So he is going to see if he can get me some r12 to recharge the system. He also says that the valves might be left hand thread as well. I think a vehicle this old I will just try and nurse it till retirement. Again thanks for the input.

If you need it, R413 drops straight in.

Chancer said:

If you need it, R413 drops straight in.

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That and Freeze12 both are better choices because there colder and have larger molecules that leak less.