Disclaimer: since owning my TR4, from 1995 onwards, I have never had the pleasure of a vent lid who would open by using the knob under the dash. The linking rod was missing. I could open it by manually from the outside though. When my car was painted around 10 years ago, I removed the vent lid and stored it in a save place. So save that I never ever have found it again . So I drove the car without a lid for a couple of years, thinking that I would find it somewhere. But that never happened, so