MG Car Repair: Right rear Tail light, mgb roadster, sidelight

Question
I have a 1979 MGB Roadster the tail light does not work on the right side. Signal works fine. The left tail also works fine etc. I tried changing bulbs in fact I took the right one out and tried in the left and did not work. I am pretty sure it is a whirring thing but I don't know where to start?

Answer
Please check that the right front sidelight works, and that the right rear brake light works.  If not, get back to me for a different answer.

Assuming it is ONLY the right rear sidelight that has failed, I think the wire to the sidelight has become disconnected.  Look inside the boot (trunk) and you will see some wires coming from the back of the tail lamp.  One of them will be coloured red.  The wire is about 8 inches long, and terminates in a bullet connector.  This connector may have pulled out, or it may have corroded.  Pull it out, clean it, and press it back in again.  You may need to prod it with a small screwdriver to get it back in.  This is usually enough to get it working again.