Bad Odor Coming from Vent

[DDiesel]

My brother is on the road. He called me and said there is a "rotten egg odor" coming through the vent into the cab on his 2002 Duramax. He says it gets pretty strong then fades away for awhile, then returns. Anything he could check besides his diet?

[DmaxMaverick]

Rotten egg = battery. Use care here, as hot vapors can be explosive. Let it cool before attempting anything. Check for wetness near the battery terminals. They can crack, leaking acid along the side. They can also short internally, causing a boil-off. In either case, it's time for new batteries (both). If they are original, it's a safe bet either/both is the problem.

[DDiesel]

Thanks for the reply. You are correct. By the time I called him back he had found an auto parts store and swapped out the batteries. One was leaking and quite warm.

[Heartbeat Hauler]

It could be the battery for sure, but I had the same problem and mine turned out to be mold/mildew on the heater core. GM tech used some kind of spray, changed my vent filters, and I haven't had the problem in over 4 years now. I was told, as well as read on the forum, that this is caused by running the A/C for long periods of time then shutting the truck down. The condensation is what causes the problem. I now turn on the A/C until it's cold then I push the A/C button so it goes off but the air coming out remains cold. And, I never run the A/C without the recirculation option.

On Edit: I just realized it's still winter time...or at least not temps requiring for A/C. Sooo, I guess maybe check that battery.... :)

[DmaxMaverick]

It could be the battery for sure, but I had the same problem and mine turned out to be mold/mildew on the heater core. GM tech used some kind of spray, changed my vent filters, and I haven't had the problem in over 4 years now. I was told, as well as read on the forum, that this is caused by running the A/C for long periods of time then shutting the truck down. The condensation is what causes the problem. I now turn on the A/C until it's cold then I push the A/C button so it goes off but the air coming out remains cold. And, I never run the A/C without the recirculation option.......

Recirc contributes to the problem, to some degree. Fresh air in is moisture out. This is why recirc will not work when defog is selected (defogs the glass quicker). It doesn't matter what area you live in, or what the humidity is, the human body will always put off more humidity (within the confines of the cab) than is in the air. Even in the deep south during the most balmy summer. If you use recirc, you are using the A/C evaporator to remove all that moisture from the air, which adds to the amount already in the outside air. The cab is vented, so moist air is pushed out as the air is pumped in, rather than recirculated. The drawback is, during the hottest times, the A/C is less efficient due to the incoming heat, rather than recirculating the less hot air from the cab. Ice-ups will be less frequent with fresh air, too.

[JohnC]

Yeah, but...

If you live in Florida, where the humidity can be 99%, recirc lowers the humidity so there's less work to do going forward. However, if the condensate drain is not working, all bets are off!

[More Power]

The 2002 models have a pair of in-cab flat-panel air filters for the HVAC system. If they haven't been changed since the truck was new, now might be a good time.... :) We have an article that explains how to do this in the subscriber area.
http://www.thedieselpage.com/password.htm

Jim

[Quack_Addict]

I'm not 100% sure but I thought GM did away with the in-cab air filters at some point. I think my `02 had one but pretty sure my `06 does not.

I have heard of guys cutting out the duct work in the later trucks where the air filter went and installing a filter as the real estate is still there.