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MG Car Repair/turn signal

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Question
My left turn signal doesnt flash, the front and back light come on but dont flash. Right signals flash perfectly and the hazards flash all 4 signals just fine. Do you have any idea why this might be?

Answer
Hi Levi,

The Lucas flasher units work on the resistance of the current going to the bulbs. Each bulb filament has a resistance value so normally the two bulbs (front and rear) supply so much load on the flasher that a plate in the flasher heats up and warps and that disconnects the lights. But very quickly the plate cools off and it springs the contacts back together thus the flash on and off. Since the right side works normally that means that the flasher is working as it should to the load of the two bulbs. And since the left side bulbs light up, that proves the wiring is probably ok and the turn signal switch is doing what it is suppose to.

This leaves one main and most likely cause. Either the front bulb or the rear bulb or both have too low a WATTAGE value and thus can't conduct enough current to make the plate in the flasher unit get hot enough to flex over and open the circuit.

There is a simple test. Just switch both front and rear bulbs of the right side with the bulbs of the left side and if the problem switches sides you know that is the problem. You can try to see if the WATTAGE rating is still on the bulbs as you switch them. But often it is printed on the glass and that gets burned away but it can't hurt to look.

Let me know,

Howard

MG Car Repair

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Howard M. Fitzcharles III

Expertise

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

Experience

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.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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