My 15 year old Maruti Wagon R has a weak AC relative to internal volume and often fails in intense Indian heat. Can I add an aftermarket AC to improve the cooling and prevent AC breakdown? My idea is to have 2 complete AC units installed to share the load in extreme heat. Only one would need to be used in cooler conditions. I could not find out whether this is feasible, despite much searching online.
There is aftermarket AC kits available, there are loads of manufactures and the kits differ depending on the applications.
Before looking into fitting in an aftermarket system I would take the vehicle to a garage with air con equipment to get the system pressure tested. Usually this procedure holds the system under vacuum for anywhere between 10-40mins and monitors the pressure.
Your option in regards to the aftermarket system seems to be:
A roof mounted electric unit - by far the cheapest and easiest solution, it can be fitted in a morning and at worst case you may need to install a second battery and split charge system and/or a larger alternator. Usually though there is no need for any extra battery's or alternators. Simply cut a hole in the roof and install.
An unfloor/dash engine driven unit - the most professional option if you want a nice 'factory' spec install. You install the matrix/blower assembly either under the dash, seat, floor or in the roof lining and either tap into the existing AC, install a larger AC compressor or add an extra one. The benefit of this system is you can get much larger cooling capacity than an all electric version. You can also get a matrix with built in heater.
I have had great success in installing Webasto products their equipment is also used in most OEM applications so that proves how well built it is.
Just google 'aftermarket air conditioning'. There are loads of kits targeted at the classic car community. Car builder solutions in the UK is just one company that springs to mind although I have never used their products.