The wonderful illogicality of the chrome bumper controls - the heat control has to be turned clockwise to turn it on whereas the direction control is turned anti-clockwise, which is the more natural direction for turning a rotary control on, I suggest. This is because both dash controls pull the cable when turned anti-clockwise, and push it when turned clockwise. However the air flap at the heater unit shuts off air flow when the cable is pushed, but at the tap on the cylinder head pushing the lever opens it for heat, and that is where the illogicality comes from. The operation of the dash control for heat was reversed on rubber bumper cars and V8s so that turning it anti-clockwise pushes the cable instead of pulling it, so then each controls is turned anti-clockwise to get heat or air, and turned clockwise to shut them off.

Showing the holes in the metal dash-mounted heat-control knobs, direction control knobs are similar. Press down the sprung pin at the bottom of this hole to release the knob. If the control shaft has rusted badly the corrosion could have expanded to jam the knob onto the shaft.

With the knob removed you can get at the nut which when undone allows the control to be withdrawn from the rear of the dash. On UK cars there should be enough cable to bring the control below the dash to access the cable clamps or for lubrication. Also shows the pegs and location holes to correctly orientate the control in the dash so the control knob legends are correctly aligned with the datum pin.

The control and its main component parts. Out of interest the multiple holes shown in the moving lever (and there are more in the fixed bracket underneath) allow a set of components to be assembled in various ways to suit many orientation and operation direction requirements. This is a 1980 heat (I think!) control.

The controls of my 73 roadster, 3/366 for heat and 3/347 for air ...

... and 75 V8, 3/533 for heat and again 3/347 for air.

Different sheath on the V8 heat control (left), and stranded inner on the air direction control (both cars).

The heater controls on the LHD cut-away at Gaydon. This shows both controls having the same orientation i.e. turning anti-clockwise pushes the cable. It also nicely shows why the controls have different part numbers and are orientated differently on the dash - the upper control has to come down past where a radio would go, whereas the lower control has to go across to fit above the turned-under part of the dash. Similarly the angle the sheath makes to the spindle varies - the upper control sheath has to pass over the cross-brace, whereas the lower one has to pass in front of it. It's pretty clever, really, that the designer came up with a method of achieving so many different orientations and angles using the same basic parts just assembled differently.

The fresh-air vents in the 73 and later UK dash. In case you are wondering about the three 'foreign' switches, the PO had rather butchered the dash to fit a couple of switches that were neither the same as the originals or each other. I was fortunate to get three illuminated switches of the same type but different colours/logos to tidy it up a bit. The left-hand one with the fan logo is connected to the cooling fan relay, so not only can I override the thermostatic switch if I want to but it also shows when the thermostatic switch has closed to operate the relay and fans. The middle switch has red illumination and is used to operate the rear fog lights. The right-hand switch has green illumination and is used to operate the front fog lights.