Answers to Why does my A/C blow foul smelling air when it first turns on? suggest several fixes that depend on knowing where in the car they are located. I can't determine in any of my cars where the following items are. E.g.:

  1. Where is the A/C drain?
  2. Is the heater core before or after the evaporator?

Without buying a service manual is there a way to determine these things for any particular car?

  • if your name relates to an issue with your car, you might have a leaky "heater core" (see image below).
    – JPhi1618
    Dec 30, 2015 at 19:02
  • What make.model/year of your car? Dec 31, 2015 at 19:39
  • @DucatiKiller - I'm interested in whether there is a general answer. So answering it for the particular car I own today won't help me when I have a different one, or when I'm trying to help someone else.
    – feetwet
    Dec 31, 2015 at 20:13

2 Answers 2


Here's an image to a cooling system for your reference.

Each vehicle has it's own unique setup. The differences in some cases are slight and in some very big.

You can see the placement of your heater core.

enter image description here

Here's another image of a general layout for an AC system.

enter image description here

A Haynes service manual is about $20. They are worth their weight in gold if that's all you have. Factory service manuals are by far the best. IMO, you would need a service manual of some type to truly be successful maintaining your vehicle.

Regarding any drain or additional detailed information about your car we would need to know the make/model/year.

  • Wouldn't that be a picture of the "Heating system"?
    – JPhi1618
    Dec 30, 2015 at 19:03
  • @JPhi1618 well, it's the cooling system for the engine which includes the heater core. I know there's a better answer to this question for sure. I'm just trying to get the OP a quick response with something and that someone better/smarter/faster is going to follow up with 'the goods' Dec 30, 2015 at 19:04
  • @JPhi1618 and when that happens I'll probably delete this one. The only value I really brought was to recommend the purchase of a manual....and cool looking picture. Dec 30, 2015 at 19:05
  • Which I appreciate! ;)
    – feetwet
    Dec 30, 2015 at 19:06
  • Hope this was helpful. Dec 30, 2015 at 22:31

Smelling A/C system can be caused by these things: dirty A/C filter; clogged evaporator; and if your A/C vent is not set on recycle mode.

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