I have a 1999 Tahoe 4dr 4x4 and have a musty, vinegar like smell coming from the vents mostly in the summer. I have looked for a cabin air filter, but from what I can find out my model year does not have one. I have cleaned the intake vents under the hood - my next task is to check to make sure the drain from the HVAC box is not plugged.... but I can't find it. Can someone help me find this?

Also - any other suggestions as to what may cause this?

thanks a bunch.

I have a 1999 Tahoe 4dr 4x4 and have a musty, vinegar like smell coming from the vents mostly in the summer. I have looked for a cabin air filter, but from what I can find out my model year does not have one. I have cleaned the intake vents under the hood - my next task is to check to make sure the drain from the HVAC box is not plugged.... but I can't find it. Can someone help me find this?

Also - any other suggestions as to what may cause this?

thanks a bunch.

You should see the drain tube by the firewall (at the same level as the manifold) and you can access it from the right fenderwell.

My '02 doesn't have cabin filters either.

You might have crud stuck in the evaporator core...here's a write up:

http://www.fullsizechevy.com/forums/general-discussion/tech-articles2/272657-improve-obs-c.html

My 1998 had all sorts of stuff stuck up in there. If nothing else, cleaning it out will probably help a/c performance. Be warned, I got a load of water on the floor using the hose like they mentioned in the post....have some towels handy.

Condensate drain line is on passenger side firewall about a foot and half from the passenger fender and mid-way down from the windshield. If I remember, it's kind of to the right and below the accumulator (silver cylinder shaped unit). It should be near the lines going through the firewall to the evaporator coil. Looking from beneath the vehicle may be easier.

If it drips when you've parked after driving around with the a/c on then it's probably not clogged too bad. Cleaning the evap coil box will help probably.

I have a 1999 Tahoe 4dr 4x4 and have a musty, vinegar like smell coming from the vents mostly in the summer. I have looked for a cabin air filter, but from what I can find out my model year does not have one. I have cleaned the intake vents under the hood - my next task is to check to make sure the drain from the HVAC box is not plugged.... but I can't find it. Can someone help me find this?

Also - any other suggestions as to what may cause this?

thanks a bunch.

my 2000 has the filter ...your vehicle if bought used probably had the filter and the previous owner threw it away , the evap inside the ducting is most likely plugged with organic material [compost pile] try to rig up a small flex hose to vacuum cleaner and with a small tooth brush suck out the debris..


when r134 refrigerent was used for a/c systems the evap passageways are made much smaller that is why now these filters are required to keep the evap from plugging up...call dealer with vin # to find out if indeed the air filters apply to your vehicle...

you all are suffering from same mistake aftereffects - improper a/c shutdown.

what happens, when you run a/c and then turn it off/turn off engine, there's a lot of condensate left ON THE CORE FINS. plus, condenaste in the ducts.
this is ideal nursery for all little critters. so, later you start getting that infamous rotten potatoe smell coming out of vents.

proper way to shut it down is to, about 2 minutes before your final destination, turn a/c off and set blower on 2, or leave it on it. what it does, it blows all the moisture away from the core fins and ducts.

donno about small vacuum and such. i did, succesfully, this: turn blower to max, open windows, and spray a ton of lysol bacteria killer into the intakes below the windshiled. takes a while for it to get into all the ducts. worked.

I don't have any smell problems in my a/c because I keep my cabin filter clean and when needed pay 20.oo for a new cabin filter.....I like to keep cool all the way to my destination...