Oil Injector, which type? how do you use?

I want buy an oil/dye injector for automotive AC use. Seems there are two types. One you use in conjuction with a vacuum pump, the other seems to have its own type of pump, where you screw the handle in, and this forces oil/dye into the system.
Which one do you guys recommend?
This is for Top-Ups and minor AC servicing use.
TIA
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On 7/11/2011 4:53 PM, Anti-Spam wrote:

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Vacuum pump? The ones I know of go between the hose and the low (suction) side of your manifold gauge set. You fill it with oil, screw the lid on, connect the suction hose, with the center port open crack the low and high side valves for a second to purge the air out of the center of the manifold and lines, cap the center port, then open the low and high side valves again with the system running and let the system's own pressure difference push in the oil.
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neither it does not work

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wrote:

It would help me if you could explain why they do not work TIA
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on the big system such as large chillers ok but on small systems it is west of timeas As I see it you probebly represent OEM of dye injection Sorry old man that is the way it is.

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