Mercedes Benz repair: a/c problems on 1984 380sl, r134a refrigerants, number search results

Question
My a/c started turning off all of a sudden.  I would punch different buttons on the a/c control and it would start up again.  On the last time it didn't cool any more after it went off.  My mechanic replaced the a/c control but the compressor wouldn't start.  Freon was added to because it needed it but the compressor still didn't start unless a test light is used.  I wonder if it is a relay, but the manual doesn't show where it is and I don't know where I can order the relay if it is only one.  The next question is how can I check for leaks since I now think the car was low on Freon.  I have a feeling the car really didn't need the a/c control - I hope my mechanic didn't mess up the a/c control.

Answer
Answer:

The most common issue with your system is both of these switches.

PART NUMBER SEARCH RESULTS WITH PRICES
Vehicle 1984 Mercedes Benz 380SL
Part: A/C Temp. Switch
 Note:  @ receiver drier
Located on receiver drier for auxiliary cooling fan. Identified by 2 spade terminals on short pigtail with red base.     
R1055-29376 A/C Temp. Switch    IN STOCK  
http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?header=header.jsp&foot...



PART NUMBER SEARCH RESULTS WITH PRICES
Vehicle 1984 Mercedes Benz 380SL
Part: A/C Pressure Switch
 Note:  
2 bar low pressure and 30 bar high pressure binary switch. This switch is designed to be compatible with R-12 and R134a refrigerants. Located on reciever-drier with 2 spade terminals. Used for compressor cut-out.     
R1054-178181 A/C Pressure Switch       IN STOCK
http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?header=header.jsp&foot...