Aircon advice

I think my aircon is due for servicing na... my ride is a 2001 Revo SRJ 2.0 with dual aircon... Malamig pa naman siya but mahina na yung buga ng hangin sa 2 center vents sa harap.. yun 2 sa gilid ay malakas naman.. advice lang po regarding this..

A guy who owns my suking auto supply w/ the same vehicle model as mine gave me an advice;

1. na kahit daw ako lang ang sakay ng Revo ay dapay nakabukas din yung aircon sa likod,para continuous daw yung flow ng lamig...

2. yun harap lang daw palinis ko, huwag ko daw pabubuksan yung vents sa likod dahil di na daw kaya ilapat ulit yun...

3. kailangan palitan na din daw yung "forgot the name"(parang nakalagay sa bilog na kaldero sa ilalim ng harap na right fender)

i need your opinions on these... :help:

you may have the same vehicle model but im sure you do not use your vehicles the same way.
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1.
yes the cabin will be cooler if you use both front and rear aircon at the same time even if you are alone. but this is also translates to more fuel consumption. = less fuel mileage.

2. have the rear a/c checked too. just tell them not to touch the vents as your friend said. it maybe dirty already and needs cleaning

3. harap ng right fender, i assume its in the engine bay. air filter?