DIY R134 Charge ?

[svcambria]

The Danfoss compressors usually have a Shroeder valve (looks like a bicycle tube valve) on the low pressure side. It is to this that you would connect a manometer (reefer gauge). If it doesn't have a valve, you will have to hire someone to remove the end cap on its small tube and re-place it with a valve (unless you want to try silver soldering). The refrigerent is lost doing this, can't be helped; also you can't introduce die into the system (to detect leaks) unless you have this valve.
First tho I would check the LED troubleshooting light which should be on your unit (if i is new enough) and see if it flashes, and what the number of flashes in the group are, and correlate that with the data sheet for Danfoss compressors. Secondly check the water circulation and water pump (you don't mention if you have water cooling as well as air). Check and see if the air cooling fan is working. And check the thermostat by removing one of the wires at the control panel (the little black box by the compressor) to see if it is stuck (if the unit turns off, you have a Tstat problem). All these are much easier to do than fiddling with the freon which in a closed system you should (ideally) not need.
Lastly, can you even buy R 134a? Kinda thought that was sold only to refrigeration specialists. It's super common in Mexico but I thought restricted in the US.
Note: you can top the system up with gas and it will work just fine unless you lost oil - which is really hard to do. And you should purge the manometer hoses by running a little bit of refrigerant thru them while screwing the connections down on the compressor.