I was told by the sales agent that if I want to start off my engine with the aircon re-circulation as "on", I will need to put the recirculation "latched on", turn off aircon and then the engine. I tried that but it won't work. Anyone knows how to do it?

 

Not sure. It does not seem to mention that option on the attached page from owner manual (you did not specify year). Some options are mentioned.

But I was amazed at the revelation on the next page in the manual, where this text is from:

 

Ok, let me make some amendment. The steps that I was told to do it to make the aircon recirculation works every time I start the engine and as default are,
1. activate the recirculate latch on,
2. turn off the aircon before turning on the engine,
3. the aircon recirculate will be defaulted from now on whenever the car is started

I tried these steps but it still won't work. I got my LR4 in 2013 and I was told that it is made in 2013 too.