Troubleshooting with Steve Rothwell

HUMBER SCEPTRE CHARGING PROBLEM

QI am hoping you can help with a problem that has baffled my local auto electrician. I have a 1966 Humber Sceptre MKII which is fitted with the early type alternator and the 4TR control box. When there is a small positive charge rate, the ammeter needle and the lights will flicker rapidly. If the wires F and Earth from the box are joined effectively isolating the control box, the flickering will stop. It was diagnosed that the control box needed replacing which I have done, but the problem remains exactly the same with the new control box fitted. Does this mean that the alternator is at fault?

Davin Edwards

A My first check would be to see that all the connections are tight and that the problem is not due to something as simple as a loose terminal. I would extend these checks to not only the alternator and ignition wiring, but also to the battery and earth connections, including the engine-to-body earth strap.

The alternator fitted should be a Lucas 11AC, which also needed the 3AW and 6RA relays. It is feasible that one of these relays has developed a poor internal connection