What should my next purchase be for working on A/Cs?

[signcrafter]

I've been slowly building up my AC tools over the last couple of years. Started out with a set of mastercool gauges. Then bought a robinair vacuum pump. Have been using the small cans with a postage scale to try and get the right weight. Picked up a 30 pound tank of r134a this week because I was sick of dealing with the small cans. I have a compressor to change on my sister's MDX soon and wondering what my next investment should be for working on ACs? A scale like this one, http://www.amazon.com/dp/B000QS2XQK/?tag=atomicindus08-20 Or what else is needed that I should pick up for this job? I usually pick up one or two new tools when working on family member's vehicles.

 

[Farmall 1066]

I'd say a scale is a good thing to get next. New systems aren't as forgiving of a "charge it till it cools good" approach.

 

[Bikes&Bowties]

Flush gun or oil injector for your gauges? I feel those are more important than a scale. Charging by weight is nice for simplicity and billing the refrigerant to a customer. But its not always as perfect as charging by pressures and temperature.

 

[mikebaker1129]

A scale .

 

[chevelle67]

A good micro gauge cause evacuating by time is about as wise as charging till good and cold.