noisy a/c compresser?

[pancholi]

1991 500sl ..over the past 3 weeks when the ac is switched on it makes an initial screeching sound that lasts about 1 second then followed by a the same sound but lasting for about 1/2 second at an interval of 20-30 seconds.
the a/c is producing cool air..
could this be at the belt pully is splipping or worse?
thanks

 

[GEORGEROV]

Belt is probably glazed and slipping even if tight. Replace with a new one. Congratulations on having working a/c on a 17 year old car!.

 

[pancholi]

belt looks glazed. will replace at next service about 2000miles...thanks