6speeddave

Looking for any input you guys may be able to provide. Have a 2015 E400 sedan with 75,000 miles. AC for several months now has emitted almost like a sweet / chemical chlorine swimming pool odor. Its not overly potent, and seems to come and go. Sometimes its right after start up, and sometimes its after driving for 20 minutes or so. Seems to be more apparent during wet road conditions? Hard to pinpoint. From my experience, when bacteria and mildew grows on the condenser coil, the smell is pungent or musty and not quite like what I am smelling. I recently replaced my cabin filter as well with no apparent change before or after. I also have ran the heat / non-ac for 10-15 minutes to try and resolve with no change.

In addition, occasionally after driving for several minutes, at random times, the ac will go from cold to luke warm and then back to cold within a matter of 5-10 seconds. I am in South Florida so the car is exposed to high temperatures and moisture.

Thanks for any input in advance.

CaliBenzDriver

A 2015 75kMi in Sth Florida....
Good chances your AC evaporator has been treated already to knock down the biohazardous growth.

Why not spray HVAC coil again with a less pungent chemical then?

6speeddave

Thats actually a great point. 60k service at the dealer 2 years ago on carfax shows "Evaporator case drain hose serviced."

Do we have a consensus about whether spraying cleaner through the center vents, in the cabin filter box, or in the drain under the car, is best?

S-Prihadi

in RED
Too bad I can not paste a smell/odour on this post , but I believe that is R134 refrigerant and compressor oil Denso ND-8 smell.
Here is what you can do. There are two test port on your HVAC system. They use schrader valve.
Go to the HP ( high pressure ) test port, it is the one closer to the bumper and is using a FATTER black plastic cap on a thinner diameter alu pipe.
Fatter aluminum pipe is always LP ( Low Pressure or suction side ).
Take a non fragrant tissue, to block the discharge gas/oil when u depress that schrader valve stem a tiny bit to catch the sample.
Smell the tissue and tell me, is that the smell u get from the HVAC vent ?



IHX means Internal Heat Exchanger

If the very same smell on the tissue is what you get from your HVAC vent...... I am sorry to say, very likely it is the Evaporator having pin hole leak.
The EVAP is low cost, the labor will make you cry big time.because it is a total DASHBOARD out of the car job and total 100% HVAC big plastic body to be out of the car too.


in GREEN
Most likely you are already loosing decent amount of R134 from your HVAC system.
Loosing a lot of R134 from an HVAC system will kill compressor eventually, because the R134 is the compressor oil carrier.
Could be a year or two from now or soon if the leaking evap is not addressed.
If your compressor die of lack of lubrication, it becomes black death. This is a total loss of the entire HVAC system EVAP + condenser + TXV and all lines/hoses including the IHX.
You can't clean the internals of today's modern condenser + evap super small micro channels.....it is a throw away scenario.


Have fun troubleshooting and I hope you find the root cause before it will do more damage.

ygmn

Sure it is not COOLANT smell?
Coolant smells kinda sweet and yet nasty to me.

Check coolant level- of low could be heat exchanger inside leaking.... Sell car if yes.or open wallet bigtime.

But I like what S-Prihadi is pointing too which is leak in AC system specifically Evap core.
Have AC pressure checked out to see if you are low. if all fine...

then have evap cleaned and filters changed and maybe a duct cleaning if possible

then add one of them rear view mirror hanging pine trees with our fave scent.

6speeddave

Appreciate you guys. I am going to start with a DIY EVAP cleaning this week to see if that curbs the smell. I will also check the smell of the refrigerant as S-Prihadi recommends. My coolant is bright pink and full, so I am not of the belief that I am getting a leak, or a large enough one for that matter.

6speeddave

S-Prihadi,

Just did the tissue test on the smaller refrigerant line. The smell is not the same as what I am smelling. I am going to try this can of Koolit cleaner tomorrow when it shows up and will report back.

S-Prihadi

Wheeewww..... that is VERY GOOD news

Quint22

I dont recall refrigerant smelling at all, pretty sure it is completely odorless and they dont put scents in it like natural gas. Now the synthetic oil they use in it does smell. The description sounds like coolant to me but everyones perception is usually different. For life of me I cant recall what the refrigerant oil smells like although I had to mess with 100s of gallons of the stuff just on random not often occasions.

S-Prihadi

It has a very mild smell the R134A
ODOR: Faint ethereal odor
Page 4 https://refrigerants.com/wp-content/.../SDS-R134a.pdf

Used PAG oil already in our HVAC system also has smell. Depending on how dry or moisture laden the oil is, it can be not so nice a smell if moisture is higher than average
as there will be acid formation in the oil.

If you want to smell R134A + PAG oil, the evacuation hose of a recovery machine has the smell of it.
I have recovered 5 cars R134A using the same hose, depending on the car HVAC compressor location and the LP + HP service port location.
I only recover from LP port for less oil getting sucked out, but some cars have a poor HVAC plumbing design and the compressor is located high and close
to the LP port, this kind of set up you can smell the most as compressor oil do get sucked out during recovery process no matter how careful you are.

Our W212, based on my M276 engine, its overall HVAC refrigerant plumbing is good. I can avoid sucking oil out of the HVAC during R134A recovery
because the LP port location is good (high enough ) and the compressor is low enough and a decent distance away and the evaporator filter drier is
also far enough and low enough.

Quint22

Interesting, my refrigerant experience was with R114 so little different. We had to change the oil periodically (think yearly). These were rather large plants however.

S-Prihadi

When one can change compressor oil, that is surely a commercial heavy duty unit. Nice.