Help please, bad smell from the air vents (W203)

[1998K]

Hoping that this is the right section, this is related to a mechanical problem I think

Sometimes I have a bad smell coming out of the air
vents, it’s a pungent smell for few seconds max for a
minute! It seems that engine run well without any
smell in the engine bay, I’m wondering to the air con
system. I still can’t realize if it depend from the
air con when is on or off, normally it’s in auto mode,
but my question are:
• Does the cooling gas have any particular smell? I’m
wonder about any loss of gas in the evaporator?
• On the W203 some talent engineer designed the cabin
air suction exactly over the battery in the engine
bay! I mean exactly over! May some particular chemical
reaction produce that sort of pungent smell?

Thanks so much

 

[Brian WH]

It is the air-conditioning bacteria giving the smell. It needs cleaning out with a special spray.

Try Wynns Airco Fresh and follow the instructions on the tin.

Moved to Interior section.

 

[1998K]

thanks so much, Do you really think I only need to clean with a suitable spay?

Bacteria really can produce a so strong smell, "pungent", please consider that this happen sometimes!

thanks so much

Marco

 

[Brian WH]

thanks so much, Do you really think I only need to clean with a suitable spay?

Marco

There are plenty of examples of previous discussion on this subject. See the one below for instance.

Smelly Aircon

 

[1998K]

thanks, and yes I confirm that I've done already a serach on previous post, but, considering my case (it happens sometimes with a really particular smell) I'd like to have some comments about my 2 particular questions.
thanks again

marco

 

[pammy]

iirc - the smell from the aircon smells like rotten eggs which is very pungent

 

[1998K]

thanks pammy, I confirm that the smell I refer is quite different to rotten eggs, it's more acrid, you feel it in the throat!

this is the reason I'm wondering about chemical reaction of the battery or a loss of air con gas!?

thanks so much

 

[Brian WH]

thanks pammy, I confirm that the smell I refer is quite different to rotten eggs, it's more acrid, you feel it in the throat!

this is the reason I'm wondering about chemical reaction of the battery or a loss of air con gas!?

thanks so much

If it is not rotten eggs, or stale pee smell then it is not the air-con. I would seriously look at the engine compartment and cabin under the dashboard, with the engine running and check for the smell, as it could be an electrical fault , with insulation burning.

 

[pammy]

Acrid certainly suggests something either electrical or chemical. I'd be inclined to look at the electrical side first as Brian suggests.

 

[1998K]

mmh engine bay look really OK, I found over the battery, it seems, some transparent stain, due to that I was wondering about some bad battery chemical reaction!

thanks to all for the help

 

[Brian WH]

mmh engine bay look really OK, I found over the battery, it seems, some transparent stain, due to that I was wondering about some bad battery chemical reaction!

thanks to all for the help

Get the battery checked, as it could be leaking/split.

 

[1998K]

yes thanks!

How can I check if the battery is working OK? Only checking the voltage?

 

[miro]

yes thanks!

How can I check if the battery is working OK? Only checking the voltage?

It is a well documented cat-pee smell caused by bacteria. There is a replacement part that should be installed under warranty and it requires the whole dashboard to be removed.

The spray method may well be the cheapest way if it works. Otherwise make your dealers life hell for several weeks.

 

[Brian WH]

yes thanks!

How can I check if the battery is working OK? Only checking the voltage?

It needs a proper "drop test" by a competent garage to see if it is faulty or leaking.

 

[1998K]

ok thanks I was wondering to check by myself the voltage but probably is better to check to a garage, thanks again for all your help!

 

[1998K]

Dear Friends, last updates, I verified the level in battery all was OK, so I cleaned well the battery surface to verity in the next future if further spot will appear out of each screw top.

I've misured the voltage: 12.5 V after a brief test as described in the W202 Haynes Manual (hoping this procedure is ok also for W203 C270cdi): fire for 30" the beam and than measure the voltage after 5 minutes, volts should be over 12.4.

Further, to check voltage with running engine, voltage regulator should keep the voltage not over 14V, mine is 14.5, may be that this is the problem? And than an over voltage on the battery may produce bad chemical reaction?

Please does some car electrician on board tell me something?

thanks a lot

 

[miro]

Dear Friends, last updates, I verified the level in battery all was OK, so I cleaned well the battery surface to verity in the next future if further spot will appear out of each screw top.

I've misured the voltage: 12.5 V after a brief test as described in the W202 Haynes Manual (hoping this procedure is ok also for W203 C270cdi): fire for 30" the beam and than measure the voltage after 5 minutes, volts should be over 12.4.

Further, to check voltage with running engine, voltage regulator should keep the voltage not over 14V, mine is 14.5, may be that this is the problem? And than an over voltage on the battery may produce bad chemical reaction?

Please does some car electrician on board tell me something?

thanks a lot

The battery hypothesis is a long-shot compared to the known bacterial cause.

 

[Shude]

The battery hypothesis is a long-shot compared to the known bacterial cause.

The bacteria smell can be eye-watering if really bad so why not pick up a can of the cleaner and try it? It's not that expensive and would eliminate the bacteria issue completely!

 

[1998K]

yes for sure I'll proceed with the air con cleaning with teh special spray anti bacteria, but I'd appreciate if someone could also confirm if the test criteria suggested by the W202 haynes manual may be utilized as reference, voltage value of 14.5 V with running engine in particulare.

any car electrician friend on board!?

 

[andy_k]

I think most alternators/regulators have an output of 14.5 volts - anything above that and you could be concerned but 14.5 is fine

Andy