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MG MGB Technical - Slight glow in brake lights from blinker?
|Somehow, the green/purple wire to the rear lights is getting an electrical pulse but only when the right blinker is flashing, cauing the brake bulbs to flash (dimly).|
The car is a 1967 GT, the following are new:
turn signal switch
plus just about every switch in the dash.
All the electrical items are hooked up. I have checked the connections several times. I did convert to an alternator.
Any ideas would be greatly appreciated.
|This would usually be caused by a bad earth where the right rear light cluster bolts to the body, can also be caused by bad connections between bulb holders and the body of the light cluster. The flasher bulb can't earth all its current directly, so some goes via the stop light filament in the same cluster, across to the other cluster then down to that earth via that stop light filament. You *will* see a voltage pulse on the green/purple, but it is an effect, not a cause. |
Usually this would be enough to stop the flashers flashing, unless you have a modern 3-pin electronic flasher unit. And it's the reason why changing the flasher type just to fix slow or non-flashing flashers is an unsatisfactory cure.
|Thanks Paul! I'll check that ground connection more closely.|
|As Paul says lights doing strange things is invariably a bad earth. I've added an extra earth wire to the front indicator/sidelight cluster, I don't like relying on a connection between mounting bolt and body particularly in an area that gets as wet as this does.|
Did you ground the lamp body itself?
|Under one of the fixing nuts should be fine. Amazing really, that one has to cut through all the paint to get a connection to earth, precisely what one doesn't need on the front wing. I didn't use earth wires here as I found I had to space the light unit forwards slightly with a nut on the studs before fitting unit to wing to prevent the chrome surround cutting into the paint, which is even less desirable. Tightening the two nuts together has given a good earth for 20 years now. Not so the number plate lights on the rear overriders, they *did* need earth wires as there are no less than seven physical junctions to get to the body!|
I had the light clusters out to clean them up and while they were out I modified them by drilling a small hole through the cast aluminium body and bolting an earth wire directly to the body using a crimped connector. The earth wire is then run back with other wires and using a bullet connector is connected to four way bullet connector used for the head lights earth (black wires). From memory I think I had to replace the two way bullet connector with a four way on the passenger side. I used a black wire to keep the colours correct. It also enabled me to dispense with the spiky nuts that retain the clusters and provide an earth and use ordinary nuts and washers. These nuts are ok in the boot on the rear light cluster where it's dry but on the front where it gets wet having something that deliberately scratches the paint off doesn't seem like a good idea to me.
This thread was discussed between 03/01/2011 and 04/01/2011
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