Sorry for the late reply. Maruti 800's AC is generally weaker than any other car. There are 2 reasons for this
1. M800 Engine is not powerful for Ac + Driving at the same time. It is a fact that every M800 owner lives with.
2. M800 uses the older AC gas (R12 gas) which is no more legal & the R12 ac setup consumes a lot of engine power, but cooling wont be that great.
Solution:
1. Costliest option is to get rid of the complete AC kit (sell it off for approx. 3K) & get a new R134 Ac kit (easily available) - total kit cost would come to approx: 25K. The ac will be much better than the factory kit but still it would be no where near i10 or even alto.
or
Easier alternatives:
1. Do not tamper the existing Ac setup, instead opt for high quality 90% VLT (transparency/ Visul Light Transimission) sunfilm for the front windshield ( & 70% VLT for all other glasses).
This will reduce the heat entering the cabin, so cooling work for AC is reduced.
2. Replace the radiator fan with a higher wattage fan (if it is easily available)
3. Avoid dark seat covers too.
The above steps can get you better AC cooling effect. The difference still would be marginal only. The last 3 steps above will cost you nearly 4K, but I highly doubt if you will be satisfied withe outcome. This post is not to discourage you, its just a word of advice - "AC in M800 is not worth spending your money".