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MG MGB Technical - indicator problem

Help.

I have just purchased a 1979 bgt, the indicators did work for the first 1500 miles but are now very slow and only flash very briefly, the hazzards work as they should. Is this a common problem with the bgt that is easily sorted or could it be more sinister, any help would be appreciated. Thanks.
jason 1979 bgt

Jason - common prob - several possible causes: tired indicator unit ( visit wrecker- get a modern unit which is not built into hazard - I use Peugeot) - Possibly low battery voltage (usual age-related issues/check the earth)- possibly an earthing problem - good luck !

Roger
Roger

Indicators/turn signals suffer from bad connections more than anthing else, the slightest reduction in current from perfect starts to slow them down, and it doesn't take that much to stop them flashing altogether.

A dicky hazard switch is often the cause of non-working indicators, which can sometime be cured temporarily by flipping the hazard switch on and off a few times. If that appears to do the trick, but comes back, then you can dismantle to switch (in a poly bag to catch all the bits), dig out the old grease and put in some fresh. After that any bad connection in the brown circuit up from the solenoid to the ignition relay, through that to the fusebox, through that to the green circuit, and in any one of the myriad connections in the green circuit to the indicator flasher unit, as well as from there through the indicator switch to the light units will contribute to slow or non-flashing. If both sides experience the same symptoms and the same rate of slow flashing then the problem is probably back from indicator switch through the indicator flasher, fusebox etc. as mentioned. If the sides flash at different rates then the slow side probably has bad connections and/or tired/incorrect bulbs, but you could also have the problems in the common part of the circuitry as well contributing to it.

The best way to locate it is to bypass the indicator unit, turn on the ignition and indicator switch (first one side then the other) to one side or the other, and plot the voltage at the battery and from the solenoid through the ignition relay, fusebox, hazard switch, indicator switch and out to the bulbs. Ideally this should be the same as the battery voltage right through but in practice even in a 'good' system the voltage will drop very slightly as you get out towards the bulbs. A bigger drop than the other between any two adjacent points is worth investigating. Also measure the voltage on the cylindrical metal part of the bulb, switching the voltmeter to a more sensitive scale. Again ideally that should be zero volts, but if there are bad conenctions between the bulb and its holder, or the light unit and the body or ground connection, you will see voltage. Note that on a rubber bumper the rear light clusters earth through their physical fixings to the wing, but the fronts have a ground wire shared with the headlights. Note also that you can get a bad connection between the bulb holder and the base of the light unit. The front light units are probably more likely to suffer bad connections from corrosion due to their exposure to wet and salt.

Some do fit a modern electronic flasher which isn't so subject to voltage and current reduction, but unless the fault is within the flasher unit itself that still leaves bad connections in the circuit which will contribute to low light output. If you *do* opt for a modern 3-wire flasher unit instead of the original 2-wire, the third wire goes to earth, and do a test to make sure it gives you the correct bulb failure warning. On the original flasher units if a bulb fails it stops flashing and the working bulb glows all the time. On modern units the remaining bulb flashes at double the normal rate. Be aware that there are some so-called heavy duty flasher units around which don't indicate bulb failure, these are dangerous for obvious reasons.
Paul Hunt 2

This thread was discussed between 18/03/2008 and 19/03/2008

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