newbie questions

[penguins25]

when you put your gauges on an ac system you lose freon every time right?
is this enough to make a difference?

is it normal to have little bubbles some times when you unscrew the service caps?
also pressure build up in the caps
is this enough to make a difference?

[JohnHere]

when you put your gauges on an ac system you lose freon every time right?

The answer is, yes, you do lose some refrigerant every time. I don't know how much, but I would guess a relatively small amount. The loss would depend on the length of the hoses attached to the manifold gauges. The longer the hoses, the more refrigerant they could contain and vice-versa. Regardless, I believe it would still be a small amount. You wouldn't want to allow the system to suck this small amount of refrigerant back in, however, as the hoses will also contain some air and moisture, which you don't want in a system.

is this enough to make a difference?

I don't think it would make any difference to a system if you tested it a time or two. Testing three, four, or more times would begin to add up, though, and would depend on the system's total capacity. If a modern system holds, say, 14 ounces (less than one pound), an ounce of loss would be proportionally more significant than on an older system holding, say, 40 ounces (2-1/2 pounds).

is it normal to have little bubbles some times when you unscrew the service caps?
also pressure build up in the caps
is this enough to make a difference?

A minute amount of pressurized refrigerant, dye, and oil under the caps is normal because the caps do the final sealing, not the Schrader valves. I think such a small amount of loss when removing the caps once or twice would make virtually no difference to the total refrigerant charge unless, once again, you removed/reinstalled them many, many times.