MG T-ABC

I ordered LED headlights from Classic Dynamo out of England.  We exchanged emails and I sent them pictures of my old bulbs, sockets, etc. I have a 1949 TC with a dippable headlight switch (high/low beam).  I installed the bulbs and can only get high beam.  I checked the power output at the light sockets and I have a bit or residual voltage in low beam when high beam is selected and the same is true when I select low beam.  I disconnected the low beam wire to both sockets and can get high beam.  I did the same thing with the high beam wire and still get high beam, no low beam.  I was thinking that I needed to add a ballast resistor to both outputs under the dash, but now I am not sure. Disconnecting the power to the back of the bulb socket, one at a time,  should have given me the same results. Am I wrong?

I'd suggest this is a more question for Classic Dynamo themselves.
Clive

Yes Classic Dynamo will sort you.  I suggest you need the use of blocking diodes for you bulbs to work correctly.
Roger Muir

Check that you have a good connection to ground/earth from the headlight. I have had some weird symptoms when I had a poor ground connection (admittedly with incandescents and not LEDs).

John Kallend - TC0845
Professor Emeritus
Department of Mechanical, Materials and Aerospace Engineering
Department of Physics
IIT, Chicago