It should put you in the ballpark. If undercharged, it will show bubbles with compressor engaged. If overcharged, you'll will not see any bubbles.

Of course, the 'bubbles' are affected by the temp and humidity. If very hot (90F) and high humidity (85%), it is possible to see bubbles in the site glass and be properly charged.

This is not very accurate and as Steve says, the charge needs to be measured to be sure. But this will give you an idea as to where you are.

You can also check my web page, Menu #14, and note the operating temps and pressures given in the table.

For example, going along at 60mph, you should typically see the EVAPORATOR TEMP SENSOR (test step #5) cycle between 37F to 43F. If so, it's doing all it can do. Of course, very high temp and/or humidity will make those numbers vary a bit.

Hope this helps!

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Regards . . . . JimF
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'94 S500 Cpe

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