The compressor does not kick in. The belt is not slipping.

Is there a way to bypass the low pressure switch just to check if the compressor works and where is the location of this low/high pressure switch

On my 82 300D T the switch is in the front lower right corner of the engine compartment. The switch is mounted on a round device with that looks like a sight glass on the top. The switch has two spade connectors on it and if you disconnect them and connect them together the compressor might engage, if it does you are low on freon. Do not run the compressor long this way. I hope this helps.

Rick

Almost certainly the system is out of gass take it to your local AC dealer and get some pressure gauges on the system or go to Kaymart or Walmart and buy the kit to check it out and refill it yourself