I am getting a foul smell when I'm taking air from outside. Note that when I turn on AC and recycle the air inside, the smell is gone.

But re-appears when I turn the AC off and start to take the air from outside.

It smells like piss. The car is about 4 yrs old.

What filter/part do I need to replace.

  • When's the last time your cabin air filter was replaced? It might be fine since the smell seems to go away when you recirculate the air internally, but it's at least a very, very inexpensive place to look first.
    – Ellesedil
    Commented Aug 14, 2017 at 18:40
  • @Ellesedil I will have to check my records. My understanding is that when they replace Air filter - that means the air filter for the engine, correct?
    – NRJ
    Commented Aug 14, 2017 at 20:01
  • 1
    Usually, yes. In my experience, the cabin air filter is usually called out explicitly. This is also something you could do yourself. At least on my Subaru (2012 Legacy), the cabin air filter lives behind the glovebox. All I have to do is decouple the support arms and the glove box will swing down to towards the floor. Then I slide the cabin air filter out and replace it with a new one and reengage the support arms of the glovebox. Hopefully, the procedure is similar for whatever model year Forester you have.
    – Ellesedil
    Commented Aug 14, 2017 at 20:10
  • Thanks Ellesedil - I have 2014 model Forester. Will try that
    – NRJ
    Commented Aug 14, 2017 at 20:34
  • Wear gloves. You are probably going to find a dead rodent up in the dash or under the hood up near the firewall. In-cabin filters can get smelly, but not usually SUPER noticable when switching circulation. But beware of removing the glovebox, there is a black plastic cylindrical supressor on the passenger side that has to come off too.
    – Ted Pants
    Commented Aug 15, 2017 at 0:46

1 Answer 1


Open the bonnet & check the vehicles fresh air intake vents just in front of the windscreen.. Clear out damp leaves, bird droppings and anything else that's in there. That should resolve the stink.

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