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MG MGB Technical - MGB GT FLASHERS

My 1975 MGB GT indicators seem to have a mind of their own. Depending on how warm the car is or how fast I'm driving the indicators vary in how quickly they flash from about 10x per minute to staying lit permanently. Initially problem was only on right where fixing a weak earth at the front seemed to improve things. Is it the relay or do I have to take out all the lamps and check the connections?
P G LIDDER

10x per minute is no good -just think of a "modern" car. It will also fail an MOT. The slower the flash the lower the current being used by the bulbs (the bi-metallic strip takes too long to heat up and bend to break the contact!!) So check each side bulbs are working, check there is good connection to each and good earth. Then look at the flasher unit. You can bench test it by connecting 2 21W bulbs (in paralell)to it and a 12V battery (ie replicating the car set up) or buy another and swap it. It is mounted on the bulhead behind the instrumnets. If you have a hazard flash check you are removing the correct unit. HTH

Michael
Michael Beswick

If both sides are slow it could be simply a bad connection in the 12v supply, which if you have hazards comes via the hazard switch in the off position and is a common cause of indicator problems. But you could equally have a combination of problems incuding bad supply, tired flasher unit, tired or incorrect bulbs, or bad connections anywhere in the circuits out to the lamps and to earth. If you bypass the flasher unit (or just leave it as it is if they don't flash with the ignition on but the engine stopped) and measure the voltage on the brown, white and green at the fusebox, the green each side of the hazard switch, both sides of the flasher unit, and the green/red and green/white wires out to the corner sof the car. On a 75 i.e. rubber bumper with separate flashers there is an earth wire from the front lamp units to the mass of connectors by the headlights. Track the voltage through the circuit and look for any significant volt drops from one point to the next, or voltages above zero on the earth wire.

The hazard flasher has brown and light-green/brown wires, the indicator flasher green and light-green/brown. Note that simply fitting a new flasher unit may speed them up, but only while it 'burns in', then the new flasher unit will slow as well.
Paul Hunt

This thread was discussed between 24/08/2008 and 29/08/2008

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