MG Car Repair: 71 Midget, hi ed, electrical problem

Question
Working on restoration.  No parking lights/taillights with headlights on.  Brakes, turn signals all work.  Any ideas where to start, perhaps the switch?

Answer
Hi Ed,
Any time you have an electrical problem you need to look at your wiring diagram (which is a road map) and take a test light and start testing from one end to the other end of ONLY one circuit that has failed. Some mechanics start at the source (battery) and work toward the load (light the don't work) others start at the load and work toward the power source. I like to start at the load and work toward the power source because I don't get side tracked down a wrong branch in the diagram that way.

You have no parking lights or tail lights so you need to pick ONLY one circuit. Turn on the parking lights and open up only one light that is not on. Either remove the bulb or unplug the wires in the back of the light and test with the test light for power on the light wire. (color coded in your wiring diagram) If there is no power, then you know it is further back toward the battery. Then check at the wiring coming from the light switch (usually the same color code but confirm that in your diagram) If still no power than check for power into the switch. Usually a brown wire but check the diagram to be sure. If you have power, then it is the switch if no power then check where the power comes from, either a fuse or directly from a power source. It will probably have power because the head lights come from the same power source and you say you have head lights. The use of this method to find an electrical problem will work on any circuit on the car. If you have power at a load and it don't work then check the ground and if that is good then the load is at fault no matter what it is a fan motor, light or what ever.

If you don't have a diagram let me know and I will put one up on my web site for you to copy.
Howard