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Although you have mentioned that the smell reappears randomly, I would still like to ask again just to ensure that it is not what I think it is. Does the smell actually reappears randomly in a moving car or only when the AC is switched on for the first time and disappears after few minutes and does not reappear till the AC is switched off & on again after a gap of say 1-2 hours?

Have they checked for damages caused by rats ?
Maybe there's a dead rat in the engine bay ! :Shockked:

The smell appears randomly in a moving car & not when the AC is switchend on. On the drive from Bangalore to Pune it was there randomly for almost half the journey till the AC was switched off mid way.

The vents have been thoroughly checked for any dead animals or insect and otherwise.

Cheers,
HZS

i had the same experience in my other new car , it is definitely the air conditioning and the fungus/molds in it . The smell should go off or you can try to fix the fungus

Tricky problem! My suggestion are as below before you escalate to Maruti.

1. Remove all the floor mats & the grey material to check whether the floor is clean. Same if you have seat back pockets, under seat tray etc. Even glove box / boot should not be spared.
2. Check the engine bay thoroughly for any dead rodent.
3. Keep some fresh cut lemons overnight and check whether the odour comes back.
4. When no one is in the car, switch on the heater for a good 5-10 mins and see if there is a difference.
5. If there are competent service centres other than your current one, give the car to them for checking.
6. If none of these yield results, shoot a mail to Maruti customer support & you shall be heard loud & clear.

Every night before parking the car, switch off the AC, and run the fan for couple of minutes and see if there is an improvement.

What kind of seat cover his car has?

How about this well-known method: After a long drive(or when engine is hot enough) turn on the AC temperature level to max in the red, fan at lowest speed, close all the vents and let the engine run for a while, say, 10-15 minutes?

oh and I think i needn't mention that getting out of the car is suggested when doing this.

Where should we begin the search for the fungus/molds?

The HVAC is generally in the circulation mode or set to auto HVAC.

Seems we will now have to do our own research to check for the possibility of something burning. Will give it a go this weekend.

Thanks, will surely suggest my friend this.

The car being Zxi+ comes with company fitted leather seat covers.

ramzsys; will try that too. Thanks.

Ok for a start check the cabin air filter (or A/C filter) that is located behind the glove box. That filter should be dry. If traces of moisture is found then you get some clues.

If there is some sort of mould or something, it would help to put the ac on and the heater on max. This is usually done as a preventive measure and this seems like a really severe case. Perhaps the best thing to do would be to book an appointment at 3M for their Germ Kleen Plus service this involves the most thorough interior cleaning job I have ever experienced. Sure it costs a bit but it's better than going through the headache of a puking kid, multiple visits to the service centre etc. :)

Check the car thoroughly for wet carpet especially in the front left footwell. It could be that AC condensate water is dripping down in to the carpet.

Remove all foot mats and boot mat purchased from an accessory shop. Under high temperature these tend to release toxic fumes.
Also little trees hanging perfume (https://goo.gl/i8GmTz) can create havoc with the ac system. This dry scent nano particles get sucked in by the system and get stuck in the inner lines of the ac system and cooling coil.

I am a DZire ZXi owner HuseinZS. Check this:

(I am assuming you already have cabin filter and have kept it dry).

1. The filter module in ZXi has 2 locations where the dust will accumulate even if you keep things spic and span.
a. The intake vent from the firewall. Pressure wash this location during monthly cleaning.
b. The interchange (recirculate / intake) module on top of the filter module. It has few foam components and redirect framework.

(For this remove the filter and keep it safe.)
2. Take a leaf blower or hand held blower (1000 W plus) and try blowing air into the vents. This will essentially push back all the dust and crap that is stuck to the evaporator coil. This method is like a blowback which will push the dust out towards the filter housing. Keep a mildly wet or moist cloth at the filter location so that all dust particles will get stuck to it. Since lot of dust will blow back from the vents, better cover-up your nose and eyes with good safety wears.

This way you can safely dislodge all particles from the evaporator end by reversing the air flow.

The costly method will be to use disinfectant foam which will fill up vents and neutralize all moulds and fungus.

Ok, having tried most of the options suggested & also constant follow up with Maruti Suzuki here is the update/development with the HVAC issue;

Sorry to say but none of the solutions/suggestions suggested here helped. What helped was the persistent follow up & arm twisting with Maruti officials.

During one of our last test drives with the GM of Maruti Wondercars, this gentle man with his experience acknowledge the smell & also linked it to the cutoff timing of the compressor. What I meant was that he correctly identified that the smell is emitted every time the HVAC compressor cuts off. So in theory the smell was prominent during early morning/evening/night when the temperatures outside is colder the Auto HVAC system cuts off frequently & the smell emits. With this understood the vehicle was taken by Maruti for further probing for three days to one of their test facilities (at Wakad/Warje not sure where).

They took various performance readings & carried out tests while acknowledging the fact that this was one of the first reported case & their first hand chance to investigate the problem. No concrete solution was provided, but we for now are content with them having not closed the case. Another revelation was :Shockked: that this is a unreported problem with all of their top end models 'ZXI, ZDI' etc of the entire range having the same Auto HVAC system.

Here can I request fellow BHPians to keenly test their Maruti cars & keep a sharp nose to detect any odd smell when the Auto HVAC system cuts off.

Earlier this month, I had given my Hyundai Accent for scheduled servicing and I had told the concerned person about smell when I turn on the AC. He told me that level 4 cleaning of AC is advisable every 40,000 kms which I had not done earlier. (not sure how I missed that earlier) So since my car was at 80,000 kms I told him to go ahead with the required cleaning. It meant placing new gas, cleaning of the filters and other components. Post that I don't get any sort of smell and AC is working perfectly fine.
They had charged me around INR 3500 towards labour charges.