1983 Mercedes Benz 300td inconsistant cooling

have you checked the AC pressure?

vacuum pressure? Pressure in the ac system? Thank you for your time and responce

actually there seems to be a connection with the auxiliary fan. I have noticed that when the fan is running is when the ac works and when it's off the ac blows warm air.

if AC auxiliary fan is shutting down, it may be low on pressure.

Sorry, but how do you check the pressure?

checking the high sure what a low-pressure side of the AC will require special tools that you can purchase at your local parts store, the more I think about it it sounds like it is low on 130-A one of the signs of low-pressure in the AC is that the compressor cycles on and off, what you could do is go to your local parts store they sell a pound can of 134-A that you can install yourself I would install one can and see what it acts like.

I'm sorry, I don't understand what the relationship is between the axiliarey fan is to the ac?

When the air conditioner turns on the auxiliary fan turns on, if for any reason the A/C compressor shuts off due to low pressure than the auxiliary fan will also shut off. That is indication that the A/C compressor is cycling if the fan is also cycling to.