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MG MGB Technical - VERY odd electrical problem

I have a '68 BGT with a VERY odd electrial problem.

When the left turn signal is turned on, the left parking light turns on, but only if the turn signal bulb is in and the parking light's switch is off. The left parking light will come on if the parking light switch is turned on and the left blinker is off. If both are on, no lights. Under no condition will the left blinker light turn on.

With a voltmeter, I measured +10 between the center of the blinker socket and the outside of the socket. With the same color probes on the center and outside, I got -10 with the parking socket when the left blinker was on. Because of this, I have come to the conclusion that the lights are grounding through each other and not to the body of the car.

Has anyone ever seen anything like this before?

-Steve

p.s. the right side blinker and parking lights work just fine.
Steven J. Korotky

Not personally, but check this out: http://www.mgcars.org.uk/electrical/sneak.html
Andrew Blackley

The ground connection between the light unit and wing has failed. Power comes in to the turn bulb but cannot get out through the ground. However the parking bulb is connected to the same ground so the current goes backwards through that and grounds through all the other parking bulbs in their holders. The current through these bulbs in series is not enough to cause the higher wattage turn bulb to light but is enough to light the one parking bulb. These chrome bumper light units, and all rear light units, do not have a ground wire but rely on the mechanical fixings cutting through the paint. All well and good on the relatively clean and dry rear units but not good on the front units exposed to water and salt. Either fit a ground wire with a lug onto the stud of the light unit with another nut, taken back to the black bullet connectors for the headlights, or remove the light units, clean the metal on the back and refit. In fact I used two nuts on each stud when rebuilding mine - one in front of the panel and one behind - so I could hold the light unit away from the painted surface a little as well as clamp securely (painted with Waxoyl beforehand) between the two nuts. Without holding it forward of the wing the chrome bezel would have cut into the paint. I used additional foam gaskets between light unit and wing to fill up the space ands stop dirtt splashing through to the front.
Paul Hunt

Withou taking over your thread My left signal works perfectly until I turn on the headlights then it blinks slowly and when I put on the brake light it almost stopps blinking. My right signal works ok all the time
Cec

This thread was discussed between 22/10/2003 and 27/10/2003

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