Thanks.
In fact I already had that one...
I decided to Email Snap-On Customer Service... and 24 hours later I have a PDF of the Operators Manual!
Kudos to you guys at Snap-on!

Now, the fun starts...
I was given 2 tanks with the unit.

I took one of the tanks, that I was told was empty, and checked it, and felt empty, but to be sure I evacuated it into the other tank... pulled a 25hg vacuum on it for 30 mins.
I then put that tank on the scale in the unit... and it read empty... so good so far.

I connected the gauges to my 190e which had a leaking sight glass on the Receiver/Dryer, so I needed to evac the R12 before replacing it.

Static pressure was 65psi with the ambient yesterday of about 60degF.
I ran the yellow hose from the gauges to the 3120. and told the machine to evac..
It pulled 14oz out.... but I discovered the empty tank has a problem... there was a slight leak at the tank hand wheel seal. I could not hear it above the noise of the pump until it stopped. I immediately sealed the tank.
I then swapped tanks, and pulled that 14oz into the other tank, which is good.
The part full tank has about 5lb of R12 in it according to the scale.

I removed and drained the old drier, I measured about 25gramms of oil, so put the same omount of oil in the new one, swapped the sensors, replaced the O rings and we were all sealed again in 15 mins.

Using the 3120, I set up the Auto Sequence to pull 25hgof Vacuum for an hour, hold it for an hour to measure any leaks and then charge the system.

Here is where it got odd...
The sticker under the hood says 2.2lb or 1kg of R12.
I tried to enter that, and I got an error... I ended up telling it to put in 16oz.

The machine did its thing, and started to charge.. I had the engine running at idle and after the first few seconds the Compressor kicked in.

After a while the machine beeped and signalled it had charged the 16oz.
At idle the gauges were reading about 225psi High side and 30psi low.

I left it overnight and today I see the static pressure is 110psi.... with half the charge that it should have in there...

Did I miss something?

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2009 Mercedes ML320 Bluetec