classicretrofit Posted January 20, 2024 Posted January 20, 2024 Heat regulators (‘Flapper’ boxes) Under the rear of the 911, a cable operated valve controls the heat exchanger output. This is either by manual levers near the handbrake or via the servo motor in the ‘Autoheat’ system. It is vital that these valves properly close when ‘no heat’ is selected by heat levers (or autoheat). If the flappers open, they will blow hot air directly into the A/C system which will severely compromise the performance of the system and confuse the climate control function of the ECU. Before you start the installation, you can easily check whether the valves are working. Get the car warm and push the levers down (or select no heat on the Autoheat system). Behind the carpet, ahead of the ‘A’ pillar, feel the 60mm pipe that runs upwards through the lower dash. A bit of leaked warmth here can be tolerated but if it is hot then this needs to be addressed as a priority.
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