Ok , so i have a small problem with my S430 - 2001 , i wanted to take it to a mech to check , but now its night so i thought some one could tell me what might be the problem

So i start the car , everything is fine , as soon as i turn on the ac or the heat ,

The fan which i think cools down the radiator , or that fan which is near the engine , facing the grill , starts making a loud noise ,
could anyone tell me what might be the problem ? and how much would cost to replace it ? now when i turn OFF the ac , the fan which is facing the GRILL stops making this noise , and when i turn it on again , the fan goes on again
the engine does not make noise at all and sounds good as always , how ever that fan makes me worry ,
please help , thank you

 

By noise, do you mean noisy from the air being moved or a noise caused by a mechanical issue? Those fans move lots of air, so you will hear the air movement.

If a mechanical sound, check to make sure nothing is hitting the fan. If not, you'll need to replace the fan.

 

The fan is making a loud noise is probably due to 3 things, the temp of ur engine is above normal (above 90) and the fan is designed to rev faster making a loud noise to cool the engine. Second, the fan is belt driven, the belt worn out in due time and makes an irritating loud noise when u turn the a/c, lastly, check the fan motor pulley, hand turn it and observe if the noise originates from it. Bearings might be worn out. replace if necessary. Do not buy replacement fan assy from ebay, they are made in china/taiwan, I learned my lesson and wasted hard earned money. Goodluck!

 

The fan is designed to run at higher speeds when the a/c is on. They move a lot of air and make a lot of "air noise" when they are at max speed.