i have a 1990 240 DL, just charged the AC system. the clutch engages but makes a squealing sound when comes on, it also starts and stops every 5-10 seconds.

thanks in advance

 

Sounds like 2 problems here. The squeal is most likely from a loose AC belt. Just need to adjust it. When you say it starts and stops every 5-10 seconds are you looking to see if the compressor is turning on and off? If so then you need some more freon. What is the low pressure reading when the car is idling at 1500 rpm and the AC on full. It should be around 25-45 psi.

 

Which type of refrigerant are you dealing with? You are messing with a very dangerous (potentially) system with a deadly gas. Do you have ANY training? A good set of gauges? And, most inportantly, very good eye protection? There should be a sight glass on top of the dryer. This was so that you could "see" the freon (refrigerant) streaks if the system was low. When a a system is converted, the R134a "full" charge is at 80% of the original R-12 volume. so you will see streaks in the glass, even at "full" R-134a charge. Also, the high side pressure will be elevated more than it had been due to the different characteristics of the different gasses. The rapid cycling of the A/C clutch indicates a low side pressure... but not necessarily just that. A host of malfunctions can cause this symptom. Blindly adding refrigerant based upon an assumption can get you killed or injured. Be VERY aware of the high side pressure. If you see it get north of 375-400 PSI, STOP THE ENGINE IMMEDIATELY, and seek professional help. No point in jumping over a dollar to pick up a penny.