The a/c ducts used to emit a musty smell especially when the compressor was switched off, but would go away after a few seconds. This time around, as soon as the a/c is switched on, a very overpowering smell of a rotting acidic fruit like oranges or grapes, and it does not go away.

I already took the glove compartment off to check on the air filter, but nothing there. I reckon something must be wedged in the air ducts. Where else should I look into?

Cheers.

Most likely cause dead Rat/mice/bat in the air ducts, call your local AC service man, bet 10 minutes or less after his arrival your problem will be solve. Color, me been there done that.

The origin of the smell is caused by fungus, bacteria and other microbes growing inside the evaporator core. The moisture-laden environment is very conducive to the growth of these organisms.

More here:

http://autorepair.about.com/cs/heatingac/a/aa071601a.htm

So what you need to do is to clean out all the cold airducts. Most airco repair shops will have a special solution for just this.

Cheers all for your replies. JOD, thanks for the link. Taking the car to the service centre was my last option. I was hoping to be able to access the airducts by myself thinking that a fruit might have found its way there and has rotten.

But you can, like the airconshops, its just a spray can with fungus killing refresher, but since you got to buy the can anyway, you might as well have them spray it in there.