Hello folks,
Here is a newbie question that I always wonder. The flaps that attached under sides of fan housing(#19 & #20 in the pic).
Click to view attachment
My car is missing one of them. I am wondering what the problem would be without it. How do they work anyway? When do they open and close?

Thanks in advance for the info and knowledge.

They are used for heater air flow control when the heater blower is on and engine
is at idle ( flaps are close) the blower motor pushes air to the heater boxes after the engine get up to speed they open and the engine blower supply air to the heater boxes.

And the Porsh enginers figured that at idle the heater blower would override the output of the egin mounted blower and disrupt airflow to the kylinders.

yup, at idle the engine fan maybe overpowered by the heater fan, and that would cuase hot air to be directed to the engines cooling needs. these act as oneway vlaves to prevent back flow of hot air into the engines fan. Id be inclined to find some and hook them up. WARNING!!! do not attempt to block them off, this will cause over heating fo your heater exchangers. the exchangers must always have cool air blowing thru them, hence this opening in the fan house to feed them. even with the heater tunred OFF, air still blows thru the exchangers, only it is dumped out over the heater flap vlave rather than fed to the cockpit.

always allow for constant air flow thru your heater exchnagers, do not block this port, however you should ad the one way valves back.


good luck

you can buy used or aluminum repro's but you have to make the pin, i just bought a large coter pin and split it in 2, 1/2 for each side, works perfectly..

http://www.germansupply.com/home/customer/...substring=flaps