Rotor arm problem
Distributor Doctor can now offer a high quality alternative to the commonly available reproduction rotor arms which have been routinely failing and leaving people stranded.
This has been a sore point for TR owners for almost a decade now, but it also affects a host of other Lucas equipped vehicles from the 1930's onwards.
Recently manufactured rotor arms have been failing because the typical "mix" used in the injection moulding nowadays contains more carbon blacking and is therefore more conductive. Still more importantly, the rivet which holds the brass inlay into the moulding is slightly longer than the original, bringing it too close to the spring clip on the underside. The high tension current, averaging 30,000 volts, is always looking for the easiest route to earth and shorts out from the tip of the overlength rivet, through the reduced thickness of more conductive plastic and the spring clip on the underside of the rotor arm, to earth out down the distributor shaft. Result - no sparks at the plugs. The situation sometimes rectifies itself on cooling, but then reoccurs with increasing frequency until the rotor permanently short circuits.
The picture on the right shows what happens when one of the inferior ones actually shorts out and you lose all your sparks. The current has burnt through from the tip of the rivet & is earthing via the wire which replaces the shaft for illustrative purposes