The Problem:
With more than 110K on the odo in the 8.5 years of my 2016 Tiago, it started to show AC issues in the past few weeks. While the unit itself appeared to be working fine, there would be suddenly no air from the vents after about an hour of driving (read AC running). I could hear the blower motor noise as well as the compressor kicking in but no sign of air or cooling from the vents. There was also ice formation in the passenger footwell area where the air filter and evaporator coil are located.
Workshop Visit:
As with most Tata owners, I was afraid to visit the ASC and took the car to an FNG AC workshop along with a friend of mine. The moment they heard my car's age & odo, they were certain that the evaporator coil (also called as cooling coil) would have clogged with dirt and needs cleaning. This has more to do with TML using a mesh filter which allows fine dust to pass through, unlike paper filters used in most cars these days. They also hooked up a pressure gauge to the low pressure port and found the pressure be fine:
A quote of 6K was given to us, requiring 3 to 5 days to remove the dashboard, then remove the coil for a thorough cleaning. I was apprehensive of getting scratches & damages to the dashboard plastics in this process. After some discussions with the FNG owner, we left the place, asking some time to think about getting the repair work done.
DIY Idea:
Later that day, my friend looked up a few YT DIY videos and shared one of them where a coil cleaning liquid was sprayed onto the coil from the "air circulation" vent located near air filter. Rather than using a spray, my friend suggested using just air compressor to clean the coil before finalizing the FNG visit. One fine evening, I drove up to his place where he had access to a small industrial air compressor and attempted the process.
Cleaning Process:
First we removed the air con air filter using the
Taparia 974 stubby screw driver which I had bought only for my regular filter cleaning activity. Then we used the compressor gun from the air circulation vent (from the side) and air filter opening (from the bottom). Since I had driven ~10km to his place, the coil already had moisture on it thereby helping with the dirt to loosen up and fall down on the carpet area. We placed a waste cotton cloth on the floor to prevent stains on my stock carpet which had no floor matting. After about 10 minutes we inspected using phone camera and found the coil it to be much cleaner than before. Tested the AC for few minutes and again used compressed air for a final ~5 minutes before re-installing air filter.
Before (missed to click a clear picture):
Air gun (from the side):
Air gun (from the bottom):
Notice the dirt on the floor area from the cleaning process:
After:
Here is a pic from another Tiago owner from our social media group with his 6 year old Tiago:
Outcome:
Right after the cleaning process, I observed much better air flow (almost 2X) through the vents and felt happy about our attempt, despite not being the permanent solution. To ensure I did not feel a placebo effect, I did not inform this activity to better half who immediately felt the chilling air flow and even reduced the temperature knob that was never touched for a long long time

.
Learnings:
I learnt a few basics of car AC systems and got an opportunity to get my hands dirty in the process of cleaning the evaporator. Also saved ~6K and avoided scratches on the dashboard. I have driven around 1000 km since then and did not face the issue yet. Will continue to observe the performance, especially during long drives and update this thread.
While this may be a temporary solution, it worked quite well for me and and went ahead with creating this thread, which might help others. Looking forward to BHPians' comments on this approach and pitfalls if any so that corrective actions can be taken.
Drive safe!