Anyone have any idea what cause like a musty sort of odor when I first turn on my defroster goes away after a few but it does get annoying.

 

Sure, you likely have some mold in your ducting. You can try spraying Lysol in all your vents above and below the dash. Mine used to have this smell PLUS it smelled like dirt too. I was relentless with the Lysol and then Febreze and it solved my problem. The musty smell IS kind of normal though...

 

You have mold on your evaporator core located behind your passenger dash. It isnt fun to get to, but you can take your glove box off and find a small channel to it. There is a cleaning solution you can find at NAPA or Autozone and spray on it. Do a google search on cleaning a evaporator core and it will explain everything you need.

 

That was what I was thinking might be problem but wasn't sure thanks so much for the info

 

Mat be that's my problem. I don't know if it is a musty smell but it smells like sour milk. The only thing that has spilled in the truck is black coffee.

 

Guys I manage a fleet of vehicles on my job. We have this issue crop up every now and then and you are right it is mildew / bacteria on the evaperator core. Advance auto sells some stuff designed for this problem that works really well that I use on the job. It is about $8.00 per can. It's been a while since I have used it so I can't recall the name of it right now (too early in the day) but it should be easy to pick up. Just ask the clerk for the A/C duct cleaner. Follow the directions on the can and one can should do it for you. One tip... do not let anyone set in the truck when you spray this stuff in the fresh air duct out on the cowl of the vehicle. I had a mechanic figure this one out the hard way!

Good luck.

 

I think the biggest cause of this is shutting down without shutting off the AC for a short period. Running the AC brings moisture into the system, if you turn off the AC a little before shutting down the ducts should dry out. I shut mine off about 1/2 mile before hitting my driveway just leaving the fan run. I never had this issue with any vehicle I owned using this method.

 

I haven't had this problem with my Dodge but with other cars I would somehow haved a clogged/blocked a/c drain tube. It would cause the system to retain moisture. I'd go underneath and mostly just push on or somehow open the tube(s). Sometimes you could see mineral deposits on the end of the tube. One time when I did this, a stream came out. The smell would fade away.