MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - head lights switch

Just got my first B . The head lights did not work Turned out to be the dash switch orderd a new one when it arived was not the same as original .only had three prongs on the back was told that it was ok to use as only three wires conected to it. When i turn the lights on to the first postion the parking and side lights come on and the head lights come on dim to. when i turn the switch on full the head lights come on and work normal ie high and low beam. Question should the head lights come on dim when the parking lights are turned on or have i got some wire crossed The car is a 70 B Cheers Mike
m jones

Something is wrong. The blue wire shouldn't have power when the headlight switch is in the first position.

Make sure all ground connections are clean and secure.
Disconnect the blue wire from the switch. Turn on the tail lights and the marker lights and using a meter see if the blue wire has power. It shouldn't.
Use an ohm meter to test the switch for continuity.
With the switch in the off position, you shouldn't have continuity between the terminals. With the switch in the first position, you should only have continuity between the terminals for the red and brown wires. With the switch in the second position, you should have continuity between the brown wire terminal and the blue wire terminal, the brown wire terminal and the red wire terminal, not between the red wire terminal and the blue wire terminal.
Check the wiring for any damage, making sure the blue wire circuit is not crossed with the red wire circuit.
Kimberly

With the switch in the off position all contacts are isolated. With the switch in the first on position two of the contacts will be connected together and the third isolated. The brown and the red go to the two contacts connected together, it doesn't really matter which way round. The blue wire goes on the third, isolated contact.

With the switch in the 2nd on position *all three contacts are connected together*. You can't have the brown connected to the red *and* connected to the blue without the red also being connected to the blue.

A US 70 B has the side marker lights powered from the headlights (blue) and ground. It's possible these are incorrectly wired and are feeding parking light power to the headlights. In mid-72 the side-markers were changed to come on with the parking lights.
Paul Hunt 2

This thread was discussed between 20/02/2008 and 23/02/2008

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.