QuestionHi I have a 78 MG BGT. In the last year it has developed a fault with the lighting. On main light beam (flashed or constant) it triggers the right hand side directional indicator lights to come on (constant not flashing).
I've stripped the indicator stalk assy. down & its all fine. When I disconnect the front RH indicator lamp unit the fault stops disconnecting the rear lamp unit has no affect. Do you have any ideas what is causing this problem. Thanks!
AnswerHi Andrew,
I tried for a long time working in shops to diagnosis by logic. As with most mechanics back then I struggled with electrical problems. Until I got interested in Radio and TV repair. I took an at-home course from RCA but only completed 11 lessons of 44. This did however give me an in-sight into how to diagnose automotive circuits.
I found it to be much more simple than I was making it. You just pick one circuit (from power to load)(battery to main beam in your case) and follow the yellow brick road (wiring diagram)(first and main tool to work on any electrical problem)
As you can see from the diagram, A brown wire brings power to the light switch and then sends power to the head light dip switch by a Blue wire (all Lucas wiring uses blue wires for head light wires) Then Blue w/white for one beam and Blue w/Red for the other beam out of the dip switch.
You probably have a parking light wire plugged into a turn signal wire at the fender or the wrong bulb installed or a short between the two.
If you don't have a wiring diagram, you can copy one off of my web site at 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
