Heater flap box question

[TeeJayHoward]

I've been staring at pictures of the flappy boxes (by the exhaust under the car) and trying to figure something out, but having no luck.

There's these triangles cut out of the side. There's a flap inside. When the flap is closed, are the triangles venting the hot air from the exhaust to atmo, or are they connected to the tube running down the car to the blower?

[fintstone]

When the triangles are open, it bleeds the hot air to the atmosphere...and when not, routes hot air to the cabin. It is not exhaust (unless you have a serious problem), it is air blown in by the engine's fan, across the engine and warmed (also cooling engine)...then routed to the cabin (or not...if the valves are open). Depending on the year of your car, there may be a separate blower in the engine compartment to assist air flow at low rpm.

[FrenchTarga]

To be precise and to answer to the question of the flap into the box: you have a vertical shutter whose axis drives the horizontal triangular shutters. Thus when you see your triangular shutters closed, the vertical shutter is open to allow heated air to come in the cabin and vice versa. We can sometimes feel heat while the triangular shutters seem open, it is beacuse it is missing a few last millimeter to fully close the vertical flap to prevent hot air to penetrate the cabin. In this case either the cable is seized or out of place or the axis is seized. In this case check your cables and lubricate everything.

These boxes are connected on both side as well explained above.

Hope this will help.