Air Con Heat exchanger

[phantomdox]

Hi guys
Can anyone tell me where the heat exchanger is located?

Problem is smelly air con, done all the usual stuff ie, new pollen filter, spray deodoriser etc but after a week or 2 the smell has returned

Spoke to a refrigeration guy and he said its common and just locate the heat exchanger for the air com and give it a good clean
Just thought i'd post here as it aint obvious as to where its located
thanks