Air conditioning problems

Hello, I have problems with the air conditioning, sometimes it throws
frozen air, but from one moment to the one to cool, someone can help me.

I have a Mercedes 300 and year 1987

greetings

You could start verifying false in the electrical connections, tell the compressor pressure and high pressure sensors (if it carries) in the cabin, take out the cooking from the Blower resistances also the one that reaches the air controls ........... if you see them with dirty corrosion, give them a cleaning with a needle or something with a tip or if you can take the pins of climatismaión is commumpecially in those of speed of the Blower and discard that ................ and if you teie