I have a 1997 C280. The air conditioning whistles (an up and down whistle). It doesn't matter which fan speed I have it set to. It's a very distracting and annoying sound. I recently replaced the cabin filter about a month ago, but this noise just started. I took out the cabin filter and put it back in, but this had no effect. Could the unit be low on freon? What should the pressure read on the low side?
Any help is GREATLY appreciated.

 

Hey there,

I haev a 94 C280 and sometime got the same sound (a vuuuuuu....) only during windshield defrost in the winter. However regarding teh AC I have an issue, maybe you could help me. I need to recharge the AC with R134a refrigerant and have got a refill kit from Autozone with a gauge. i found the low pressure port just under the engine and has a black cap on it.i tried to match it with the hsoe but would not fit. any suggestions on how to proceed and refill it ? thanks

 

Are you sure you had the low side? If the pipe on the car was to big it is the high side. Also, the hose on your Autozone kit will be hard to push on because the ac system is under pressure.