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MG MGB Technical - Different Blinker Blink Speed

Why does my left blinker blink at twice the speed of my right blinker? They both have new bulbs and I have even run direct grounds to both light sockets to test them -but there was no difference? Could the blinker flasher unit be causing this effect? If not, then what else?
Robert Browning

Robert. My experience is that this only happens when one light is burned out. Are both lights on each side working properly? If so, it would be interesting to hear what others may have to say. Paul Hunt is, probably, the most competent of us in this area. He has helped me, quite greatly, over the years in understanding things electrical. Les
Les Bengtson

Robert - There are a couple of reasons for the difference in speeds. First, check the type of bulbs you have in both brake lights and both turn signal lights. If you find a bulb of different type (or even make), change it to match the other bulbs. Any difference in resistance in any of the bulbs will change the flasher rate. Second, if all the bulbs are the same, then check the connectors to each of the lights for any corrosion. It wouldn't hurt to clean all of the connectors. Check the ground for each light and insure that the ground points are cleaned to bright, shiny metal. It will make a better ground connection if you coat the surface with Kopr-Shield a
conductive, anti-corrosion surface compound,
Thomas & Betts P/N 201-31879. Finally, if all of this fails to cure the problem, check the actual light sockets to see if the crimps that hold the sockets are loose (allowing the socket to turn on it's mounting). If they are loose, replace them. Good luck - Dave
David DuBois

Hi..

Don't forget to check the side repeater lamps if you have them.

Don
Don

Great suggestions. I know that the blinker bulbs inside the car work fine and are new and the same type. I am completely restoring the inside of my car and have cleaned all connections and light sockets and wiring. I have not checked the lights on the outside of the car, but will this weekend - thanks for these great. I will let you know what I find. I do know that all the outside lights operate, but I am not sure of the condition of the sockets and bulbs. The other question I have, which may sound and be stupid, but if the flasher unit in the car is working, then it is working - correct? It should either be working or not working, but not cause
this type problem? Right?
Thank you.
Robert Browning

Robert,

There is some chance that the problem could be a problem external to or within the flasher unit. A change in capacitance in the unit or in a connection could cause it to flash at a different rate. My basic electronics are a little rusty, but I think the capacitance would have to decrease to make it blink faster. This would occur if there was a partial short circuit in or external to the unit.

Cheers, Doug
Doug Keene

Doug - If the flasher unit was the cause of the problem, both sides would flash (or not flash) at the same incorrect rate. The flashers for the MGB work with a bi-metalic blade, so capacitance doesn't have any effect on the rate. I believe that you are thinking of the electronic flasher units. Cheers - Dave
David DuBois

If you are certain the bulbs are the same all round and you have tried connecting a known good ground to each lampholder and it made no difference then that leaves the connectors between the turn switch and lampholders, or possibly the switch itself. If the right side is slow check the connectors in the green/white wire where the main, rear and gearbox looms join at the back of the right-hand inner wing, and those at the lamp units themselves. If still no joy link the two terminals on the flasher unit so the lights glow continuously then take careful voltage measurements with a digital instrument at each corner. A low reading at one right-hand corner indicates a bad connection, measure again at its bullet connector (both sides), and again where the looms join.

Of course, if it is the left side that is fast rather than the right side that is slow, you should be looking for something drawing too much current.
Paul Hunt

Yes, it is the left blinker that is faster. However, it seems that the left blinks at what I would consider to be a normal rate, while the right is extremely slow.

What suggestions do you have for checking something that is drawing too much current?
Robert Browning

Check the voltages first and if different look for bad connections as above. If they are much the same side to side then put an analogue (digital can be unpredictable) voltmeter in place of the turn flasher and with the ignition on operate the turn switch to the left. You should see 12v and the lights won't glow or flash. Remove *both* bulbs on the left and the voltage should drop to zero. If it doesn't something else is drawing current, start pulling connectors until you isolate it. If the voltage shows zero with both bulbs out then swap the bulbs with the other side and see if the fault moves. If so it is a bad bulb, but this is one of the easiest things to try early on anyway.
Paul Hunt

You could have the wires to the bulb crossed. Dual filament bulb have a different wattage rating for each filament.
R. L Carleen

Not really likely, the standard flasher is so sensitive to current that a tail light bulb would make it light up but not flash that side.
Paul Hunt

This thread was discussed between 26/04/2003 and 01/05/2003

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