Actually, everyone offering this "A/C" service in Lahore or anywhere is total and utter crap. You are absolutely right: The only time the evaporator coil needs to be cleaned is if it does NOT have a Cabin A/C Filter. Even so, I would NEVER get it serviced every year, unless you make absolutely sure to replace the receiver drier.
One thing I was going to say is, everyone should do this. Check your sight glass on the high side line and see if any bubbles are coming. If there are bubbles coming, that means your R134a refrigerant gas is low. What I can never understand is, I have NEVER EVER seen any A/C repair workshop refill the R134a by weight. That means, actually weighing the gas and recharging a car by that. In fact, underneath the bonnet of say a Toyota Vitz, it will say in Japanese to "Add 100 +- 50 grams after the bubbles have disappeared on the sight glass."
What people do not understand here is that, if you have less R134a refrigerant gas, the compressor will be working all the time and will overheat, and then your compressor will fail. I check my sight glass every season to make sure that it is clear. I have done a lot of A/C work myself because I am sick and tired of all the bull*$#% mechanics in Lahore, INCLUDING the Toyota Dealer, telling something else. I have worked on my own car A/C, along with countless other friends cars and I have well and truly sorted their car out, according to their respective service manual.
If you want to check the sight glass on the Vitz, you should look for a A/C pipe with a plastic cap marked "H". The cap is grey colour and is usually on the right side of the car, next to the headlamp. Turn your A/C on, with the fan blower at full and let it run for 5 minutes. Check the sight glass and see if it is clear or if you see bubbles. If you don't see any bubbles and your temperature is very cold, then you are good to go. If you have bubbles, let me know and I will guide you step by step with what to do. Happy driving!
