QuestionQUESTION: I HAVE A 78-B. WHEN I TURN THE KEY THE DASH AND RUNNING LIGHTS TURN ON. WHEN I TURN THE KEY OFF, THE ENGINE DOESN'T SHUT OFF.
ON ONE OCCASION WHEN I TURNED THE HEAD LAMPS OFF, SO DID THE MOTOR. IT CRANKS UP, WITH NO PROBLEM.
ANSWER: Hi Seth,
Your symptoms are useless information other than you have an electrical problem so you need a few simple tools and some work to do.
First you need a wiring diagram of the car and a 12v test light or a voltmeter. If you don't have a diagram let me know and I will put one up on my web site for you to copy.
I found that when you have an electrical problem you need to trace ONLY one circuit that has a fault. You need to trace it from it's power source to the end load (what ever it operates)
You need to trace which ever circuit is consistent, meaning it is doing wrong all the time. If none of them are wrong all the time and each is just at times, then you may need to disable part of the electrical system for a test. for example, You said when you turn on the key the dash and running lights come on (even with the light switch in the OFF position??) There normally is no way for the lights to turn on when the ignition key is turned on, so first place I would work is to disconnect the light switch and drive the car to see if the lights still come on at times. If so then the problem is probably a short in the wiring harness and then you look at the diagram and see where the light wires have a connector and disconnect the lights there and again drive the car until it does it again. This method isolates the problem in a smaller and smaller area until you are able to find what is wrong.
This is only an example of how to locate the problem. Yours may be different. So first tell me if any of the symptoms happen all the time.
Howard
---------- FOLLOW-UP ----------
QUESTION: Hi Howard, thanks for the quick response. The dash lights, and the motor running on are happening all of the time.
Seth
AnswerThat's good as it is easier to find when the problem is consistent. Since the lights are on when they are not suppose to be on, I would trace that circuit first. Look on your wiring diagram for the dash lights circuit and trace that from any one of the bulbs while they are on but be sure the light switch is off. By following the circuit on the diagram with your test light you will arrive at a power source (which it is not suppose to have, since the light switch is off) If you don't have a diagram go to my web site and copy this one down.
http://mg-tri-jag.net/78-80MGB1x1.jpg for the diagram and
http://mg-tri-jag.net/78-80MGB21x1.jpg for the index to the diagram.
Howard
