The XJ6 thankfully retains the classic triangular front ventilator windows inherited from the Mark II and earlier saloons. The early 1960-style windows were opened by simply undoing the latch and pushing or pulling them open or shut. For the XJ series, Jaguar elected to “upgrade” the ventilators with an open/shut twist knob that eliminated the fastening latch entirely. The only apparent advantage is that the XJ window can be opened to all angles; previously the ventilator moved in incremental “clicks” that prevented wind resistance from changing the glass position.

Drawing of large vent twist knob

The disadvantage is that a large twist knob must be placed on the door panel, and Jaguar didn’t give this much design thought.

The black plastic knobs — Jaguar part numbers BD35943 (knob) and BD35953 (metal cover) — remain available in the aftermarket for about $20.

But instead of replicating Jaguar’s original plastic faux pas, there is an alternative opportunity to re-imagine the door and upgrade the decidedly cheap looking black blob.

New knob design (left) displays a Jaguar logo

The original knob (see right panel above) has a thin metal cap that snaps in to cover the fastening bolt underneath. It looks quite plain and undistinguished compared to the chrome fittings elsewhere on the door panel.

Jaguar knob cap design

Our new knob design starts with a more robust “Jaguar” cap but it still must be removable so that the hidden bolt that attaches to the ventilator turning mechanism can be tightened down. The cap has a very small indentation just visible on the right side that allows a small screwdriver to lever it up if necessary.

Knob structure showing slotted shaft

The knob hollow shaft — a bolt passes through it — contains a slot that fits into the turning mechanism. The shaft must be a precise length so that the knob’s position is correct in relation to the door panel.

To keep the weight down, the internal structure of the knob body is webbed, not solid, but still strong enough to handle turning stress. Indents around the edge will improve the grip over the original Jaguar thin plastic knurling.

Proposed knob face