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MG Car Repair/turn signals


QUESTION: I have a 1977 MGB.  Turn signals don't work.  All other lights work including emergency flashers.  Have replaced fuses, lite bulbs checked all grounding, cleaned contacts, etc.  Still no signals.  I read there is relay under glove box and under center dash.  Can't locate either.  Does switch need replaced or am I missing something simpler?  Looking forward to answer!

ANSWER: Hi Jeff,

The power to the turn signals is from the Hazard switch pin #7, Green wire to the turn signal flasher unit and on to the turn signal switch by a Light Green w/Brown tracer wire and on to each turnsignal lights by a Green w/White and a Green w/Red tracer wires.

If you don't have power to the turn signal switch on the Light Green w/Brown tracer wire, check the power to the flasher unit on the Green wire from the hazard switch. The turn signal flasher unit is usaually on the fire wall behind the Speedometer and Tach. If you don't see it follow the Green wire from the Hazard switch as it goes directly to the turn signal flasher unit.


---------- FOLLOW-UP ----------

QUESTION: I followed your information.   I don't have power at the turn signal switch.  I do have power at the flasher unit on the green wire.  All connections on flasher unit have power.   The key is on for these readings.   Now what do you suggest.   Your help is very appreciated!l

ANSWER: Jeff, All the time I worked in dealerships on Electrical problems I learned one thing that is important and that is you need a wiring diagram to do any electrical work.

Since the power to the turn signal switch only comes from the turn signal flasher unit and you have power into and out of the flasher unit then the wire from that flasher unit to the turnsignal switch must be disconnected somewhere. The only connection between the two items is the turnsignal switch multi plug.

When doing any kind of tracing of power or grounds in any circuit I always test at the "Load" (item that don't work) and with a wiring diagram I test at each joint in that circuit heading toward the "Source" (power supply). Using this method of testing, it is impossible to fail to find the problem.

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


---------- FOLLOW-UP ----------

QUESTION: I think I could use that wiring diagram.  I checked for any unpluged or loose connections didn't find any.  There is an open terminal on flasher unit could that be problem?  The green wire with brown is there and goes into the the multi plug and seems tight.  I'll look for your wire diagram on your site.  Thanks

Jeff, looking at a plug connection tells you nothing. You MUST test the plug terminals with a test light to see if power is getting to there or not. !2v test lights are available at any auto parts stores and are very inexpensive. The test light and a diagram are necessary tools to do any electrical work.

The diagrams are up on my web site for you to print out. The 76 MGB and the 77 are the same except for a supliment diagram. The 76 diagram is at,   (diagram)  (index to diagram) (supliment to 76 diagram)


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Howard M. Fitzcharles III


MG from 1956 (USA versions only) up and Engine theory.


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Associate member SAE EAA member

Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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