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.:
Without buying a service manual is there a way to determine these things for any particular car?
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.
Here's another image of a general layout for an AC system.
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.
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.
