Stinky air on Econ setting -- 1995 DeVille

[MrMagoo]

Greetings, all:

I just got a 1995 DeVille, 4.9-liter, 88k on it. I love almost everything about it, except in Econ mode, the vents put out a very strong, stinky smell. At first, it reminded me of tuna fish, but later I thought...hm...might be coolant. The Auto setting for A/C is just fine; the smell only happens in Econ mode.

Now, I'm VERY new to doing anything on cars other than changing wiper blades, but I'm wondering if it's the heater core, from what I've read elsewhere. I haven't been able to find this specific thing happening to anybody else, and I've done a fair hour of Googling.

Any help would be appreciated. Thanks!

[Cadillac Jim]

Without smelling it myself, I can think of two things: clogged condensation drain hose, or seepage leak in heater core. Others with more experience with the problem and in disassembling the under-the-dash portion of a Deville HVAC will have more to say.

[MrMagoo]

Thank you kindly -- I'll start with those two things.

[Logan]

Musty smelling HVACs are nothing new.

I've never heard it called tuna though.

Some latter cars you can enable a afterblow mode on the HVAC system. Either with a Tech2 or using the on-board features. Pretty sure GM sells a a kit to install the afterblow feature on non-equipped cars that do not have the option available.

There are some TSBs....

http://tech.corvettecentral.com/2010/03/hvac-odor-technical-service-bulletin/

[Cadillac Jim]

The TSB for your car is #53-12-12A: AIR CONDITIONING ODOR AT START UP IN HUMID CLIMATES - (Dec 1, 1996). It's on my 2011 SI DVD but the figures are not. It advised to use an aerosol, P/N 12377951 (AC DELCO 15-102) to disinfect the evaporator and to install an afterblow module, P/N 12370470, (AC DELCO 15-8632).

According to TSB #91-12-04A: A/C ODOR PRIMARILY UPON START UP - (Nov 8, 1996), your car has an afterblow capability that can be enabled, possibly through the HVAC buttons and DIC display that you use when you run the OBD codes.

I have just found that the 2011 SI DVD runs under Windows 10.

[MrMagoo]

It's definitely not a musty smell. It's pungent and fishy, and it only happens on Econ setting, not when the A/C is running.

But...I did try the Econ setting yesterday and the smell seemed to be mostly gone, all on its own. If it comes back, I'll take this info to my mechanic and see what he thinks.

Thanks again, everyone.

[Z15]

Anytime there is odor from the AC, its mold and or mildew causing it and you have to disenfect it to rid of the odor. Mold can make you very sick.

[jndnaps]

I have the same problem with my 96 DeVille. It smells like coolant when I run the A/C on low only. I also notice a slight film of something on the windows and the woodgrain on the dash, but that takes a while to build up after it's cleaned up. My guess is a tiny pinhole leak in the heater core or a hose to it. I've been meaning to check it out, but been very lazy lately..

[MrMagoo]

I've noticed film on the window, too.

Thanks again for the help, everyone.