That said,
IF the Low Side Line (larger tubing into Compressor) gets Cool pretty quickly and the High Side Line (smaller tube exiting Compressor) gets Hot pretty quickly, then the Sealed System (Compressor, Lines, Coils) is very likely to be OK.
Better still, look up the RLA (Running Load Amps) that's listed on the Coleman unit label, maybe on the Compressor itself. Then start it up and measure actual Amp Draw with a Clamp-On Ammeter along the lines of this:
![](https://images-na.ssl-images-amazon.com/images/I/41sQt+0+-SL._AC_US218_.jpg)
If Actual falls within an Amp or Two from Spec, Compressor is VERY likely to be running OK AND Correctly Charged.
FYI - Meter I pictured is "Amazon's Choice" in these at about $26.00. Looking at its specs, I wouldn't pay that for the limited capability it has. Basically an AC Ammeter (can't read DC Amps) and a Basic DVOM (Digital Volt Ohm Meter) that can't read useful things like Capacitance (A/C troubleshooting) or Frequency (Generator troubleshooting). I'd stick with my cheap Horror Fright Clamp-On at half the price, OR spend more for one that does DC, Capacitance, Frequency. OR even more and add the "true RMS" measurement of AC Voltage, along with "Peak Inrush" that'll trap an A/C's max starting Amps. The "Hold Button" the cheap units have, is not capturing peak. It only locks the reading so you can reach into something, catch the numbers, then pull the meter back to see what it says.