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MG MGB Technical - indicator and hazardlight

When switched on, my indicator and/or hazardlights are only flashing when engine is running. If engine is off they stop blinking and are burning constant without flashing. Is this normal? some say it is.
My car is a 1976 RB MGB

What to do about it? If have checked all wiring inclusive the earth parts.

Best regards, Jacob
Jacob Halma

When activating the Indicator lights, (turnlights) it does not make any differance between left or right.

best regards, Jacob
Jacob Halma

Whilst it isn't normal it is quite common. The standard indicator flasher is very sensitive to reductions in current and voltage that can come about through very slightly bad connection in the myriad connections in circuit. If both sides are the same, and both sides flash at the same rate with the engine running, then it indicates (ho ho) that the main problem is in the common wiring. This comes back from the common contact in the indicator switch, through the steering column connector, the indicator flasher unit, the hazard switch, sundry bullet connectors, the green circuit fuse onto the white circuit, the ignition switch to the brown circuit, and down to the starter solenoid. The most common cause is the hazard switch, this is rarely used, the grease hardens, and becomes more of an insulator than a lubricant. You may fond that turning the hazards on sometime you may only get one side or the other flashing, and the indicators may not work at all when they are switched off unless they are flipped on and off a few times. If you have the older larger rockers with the rounded corners these can be dismantled (in a poly bag to catch the bits), the old grease dug out and new put in, and reassembled with some success. I've had less success with the later smaller rocker switches with the sharp corners, having had to replace a couple of these.

You may be tempted to replace the indicator flasher with the same type, and it may work for a while, but these 'burn in' and you will probably find the same thing will start happening again in a few weeks.

Some people get a modern 3-terminal flasher unit (the 3rd terminal goes to earth) as these are much less susceptible to voltage and current variation, but be aware if you have bad connections to start with you will still have them afterwards and they will be contributing to dim flashers. Also be aware that some after-market or so-called 'heavy-duty' flasher units don't have the safety feature that they should have, in that they don't give an indication of failure if one of the bulbs at the corners of the car should fail. With the original flasher units the symptom is that one side flashes normally but the other (with the failed bulb) only glows, with the modern units the remaining bulb and tell-tales flash at double-speed (unfortunately some drivers are too stupid to know what that means, so drive on regardless).
Paul Hunt

If you replace the flasher for the directionals get one rated for (2) bulbs. Many of the heavy duty units are rated for more lamps, this requires a larger current draw to make them flash.
J Heisenfeldt

Thanks for the reply on my thread,
I had a quick go (switch on and off lots of times) at the hazard switch this morning,
resulting in when,
-contact off,hazard is OK, indicator nothing at all
-when ignition on, nothing happens with hazard and indicators.

Paul, this may indicate that somethin is wrong somewhere in the common circuit, I will look in that direction further.
Keep you posted, Jacob
J Halma

So far so good, made some major improvements.

Cleaned my hazard switch, wich where exactly as Paul mentioned (hardened grease)
Also cleaned the indicator switch, could not notice any heavy polution there.

The result of this action is that now the hazard lights are working the way they should under all conditions.
The turnlights are now with ignition ON(engine OFF)on both sides flashing.(slowly). With engine ON they are flashing normal.

Did not check the ignition switch yet, ... Have a go at it next week.

best regards, Jacob
Jacob Halma

The turn signals are going to flash slower with the motor not running since the alternator is not charging.
Kimberly

Check the wattage of all the bulbs. Turn bulbs should be 21W.
The hazards should be drawing power from the permanant live side of the fusebox, the turn signals from the switched side.
Allan

This thread was discussed between 17/07/2008 and 20/07/2008

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