79MGB Ignition Switch

I have a 79 MGB. the horn, radio, and map light sometimes quit working, and when i giggle the key, they start working again. Could this be a problem in the ignition switch? Also, my backup lights do not work, but i believe the bulbs are good.

Thanks

You believe the bulbs are good?
With the ignition switch in the run position (motor not running) check to see if you have power to the sockets. Check the reverse light switch on the transmission. Make sure the ground connections are clean and secure.
If there has been no changes to the wiring, the ignition switch has nothing to do with the map light and horn. Use a meter or test light to see if you have power to and from the fourth fuse. Test the fuse box at the terminals where the purple wires and brown wires connect. Since it is an intermittant problem, you are going to have to test the connections and wiring when things aren't working.
How is the radio wired? Does the radio work if the ignition switch is in the accessory position? Have you checked everything else to see what else works or does not work?

You are going to need a test light or a multimeter and a copy of the wiring diagram. Wiring diagrams are available at http://www.advanceautowire.com click on stock schematics. Make yourself two enlarged copies, one for reference, and one to make notes on as you check the circuits.

My76 MGB had mysterious electrical problems which I narrowed down to a defective fuse block on the passenger side of the engine compartment. Even with good fuses it had intermitternt continuity from one side to the other. I replaced it with one from Radio Shack and solved many problems.