Air stinks when blower is turned on

The cabin air smells real bad (something like old milk) every time I turn on the blower regardless if the A/C is on or off. I changed the cabin air filter (first time in 5 years) but the air still stinks. I pulled the heater core thinking there might be a coolant leak but the core was fine. Any ideas?
2001 Grand Caravan Sport

Probably mold or mildew in the system. Buy a can of LYSOL spray deodorizer, start car, turn on vent system (outside air ) and start spraying the LYSOL into the air intake in front of the windshield, if it is mold/mildew that should take care of the problem.

You pulled the heater core - didn't the dash have to come out for that? If so, take the HVAC case apart and check the evaporator area and the blower motor. I've heard (not verified myself) that there is a drain tube through the fire wall right where the blower motor is, and that if that drain tube clogs, water can build up in that region.

Heater core can be removed without pulling dash. Been that way since 96 M.Y.

Thanks for the advice.

Yes, I pulled the heater core without having to remove the dash. But I did have to remove the stearing linkage and the brake pedal to slide the core out.

Anyway, I blew some compressed air into the evaporator drain to try and break up any blockage. I then turned the A/C on and within a few minutes water was dripping out of the drain. But it was draining before I blew it out. I also tried the Lysol but the smell stayed (although with a refreshing hint of lemon ).

I drove the van around for about 30 minutes with the A/C on high to try and clear the smell. No luck with this. I then stopped at a A/C shop and talked to the mechanic. He got a sniffer and verifed it is a leaking evaporator. He wants $900 to replace it. He said he has to take the dash out.

Anyone ever replaced an evaporator? I sure don't want to spend that kind of money.

Noticed that my Haynes repair manual does not provide instructions on how to replace the evaporator.

Hold on a minute. We're talking about two separate issues here:
1) Evaporator is leaking (supposedly)
2) Smell from blower

These are two separate issues. If the refrigerant (not sure what R134a smells like) were leaking at rate sufficient for your nose to pickup and be anonoyed with, it should have all leaked out in about a day, which means your A/C would not be working worth a hoot by now. Something tells me that the tech may have mis-interpreted the sniffer response.

Secondly, even if the smell was coming from the evaporator, as long as your A/C was still working fine, it would imply more that the evaporator needed to be cleaned (although if I went through that much trouble to pull it out, I'd replace it anyway), not that it had a leak. I'd be wary of a mechanic who pointed at a refrigerant leak as the source of stinky vents. If his intent was to replace the evaporator and planning to find and fix the source of the mold/mildew smell during the job, then he should have said that. I'd be skeptical about you having a leaking evaporator though if the A/C still cools well.

If you remove the blower resistor, would that give a small amount of access to the evaporator? If so, I've heard of people connecting a garden hose to some 3/8" tubing to make a miniature pressure washer and blast the evaporator. Then spray it with bleach water to kill any mold or mildew. Then make sure all the drains are clear.

If you do replace the evaporator, be aware that you need to have the refrigerant evacuated prior to disconnecting these lines so you don't vent the existing charge into the atmosphere. You'll probably need to stop by an a/c shop to have them evacuate the system using their recovery machine. After you're done replacing the evaporator, you can stop by the a/c shop again to have them recharge, or rent a vacuum pump and gauges and charge yourself.

Get yourself a factory service manual if you're dissatisfied with the content in the Haynes manual. Well worth the added cost in my opinion. It's the first thing I buy after acquiring a new-to-me vehicle.

Chad