Moss Motors, Ltd

I have a 1976 MGB roadster, whenever i have the front left turnsignal on and i hit the breaks it stays on but does not flash.  That and if the lights are on it stays solid too.  I checked and cleaned all the connections.  Anyone have any advise for me? 

My guess is that there is a problem in the column switch. The contacts there should remove the brake light voltage from either side if the turn signal is on that side. Sounds like that function isn't working correctly and the brake voltage is overriding the flasher keeping the lamp on. Since the dirctional lamps work ok with the brakes off and the brake lamps are ok on their own, it's got to be the switch. They're not cheap and if you're careful they can be disassembled and cleaned which may restore the function. If you do try to repair it be warned that there are springs and detent balls inside so watch carefully when you remove the cover and work in an area where you can find anything that flies out.

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'73 Midget (V6)
'59 MGA (I6) under construction

"There is a fine line between a hobby and mental illness"

The turnsignal and brake lamp circuits are completely independent, so it's not a turnsignal switch problem. I'm thinking that what may be happening is that there is a problem with the tail lamp grounding, which is causing the stop lamp to ground through the turn signal bulb.

 The tail lamp assembly is grounded through special mounting nuts that have sharp edges designed to cut through the paint. If you car has been repainted recently these nuts may not have done their job.

If the rear lamp assembly does lose it's ground, the stop lamp current can find a path to ground by backfeeding through the turn signal lamp, or side marker lamp filaments, then through the harness to the front lamp ground, which is hard wired. 

It's always worth checking the rear lamps any time there is a strangeness occuring in the TS or stop lamp circuits.

good luck 

 

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Kelvin Dodd
Global Sourcing Engineer
Moss Motors, Ltd.
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Disclaimer: Working on automobiles is inherently dangerous. Moss Motors, Ltd. is not liable for injury or damage due to incorrect installation or use of their products. All products are sold with the understanding that the safe and proper installation and use of the products is the customer’s responsibility. Follow factory workshop manual procedures and instructions, but use current shop safety standards and common sense. Some tasks will require professional advice or services which Moss Motors cannot provide.