Hi, this might sound straightforward to someone but although both headlights on my 1958 Morris 1000 work when I press the footswitch to dip the lights only the drivers side light stays on. The nearside dipped light goes off!! I have tried changing the bulb, that's not the problem. Looked at the earths and sanded where possible back to metal and replaced, Checked all terninal connectors and they seem fine.... Might the problem be easily remedied??
As both main beams are working the earth side is OK.
If you have one use a meter to test for 12 volts on the wires going into the headlamp then follow the wires back till you get 12 volts.
It may well be worth running a wire from the battery direct to the wiring coming out of the headlamp to be sure the bulb to holder is making a good connection.
Someone will be along shortly who knows what colour wire you should be looking at.
Well - blue/red is dip beam and blue/white is main. Does sound like bad connection - the advice to run a jump wire to check the lamp connections is good! Easy check is to swap bulbs from left to right, but i'm guessing you have done this already.