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Hazard Warning Switch Buzzing - A Cure


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Ever since I've had my car (a Classic VX), switching the hazards on and off has resulted in a nasty buzzing noise from under the dash as the switch passes through the midway position. It was a bit alarming the first time it happened, but a quick internet search revealed it was a known feature and unlikely to be a sign of a deeper problem. Various theories were put forward (and even one suggestion that CC had fitted a buzzer but couldn't remember why !)

Well, a year on I've finally got round to looking at it and it just turns out to be a fairly basic design problem...

Switching on the hazards connects four pins on the switch together - the output of the flasher unit, the left and right indicators, and the warning lamp.

The problem arises because these connections are not made simultaneously, but in two stages via a sliding contact. Somewhere between fully 'off' and fully 'on' the flasher unit is connected to just the warning lamp. This is far too small a load for the flasher to work properly, but it tries its hardest and 'flashes' so fast it just screeches.

In the diagrams below the warning lamp is shown separate from the switch for clarity and  'H' represents the contact block:-


I don't know how common this problem is. (?) Probably not all makes and ages of flasher units behave the same way with very light loads, but for those who do suffer from it there's a very simple fix... Just swap the flasher/warning connections with those for the left/right indicators as per the diagram below:-


Now in the intermediate state only the left and right indicators are connected together, and there's no load on the flasher unit until the switch is fully on. Hazards can now be switched on and off without further embarrassment...



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>>Is it easy to get the female connectors out of the loom plug?<<

Looking down the hole in the housing from the open end the brass contact has a single rectangular barb on the opposite side to the split which need to be pushed inwards toward the centre while gently pulling on the wire.

A tubular type extraction tool is best but a small watchmaker's screwdriver is fine, but then it's easy to push the barb in too far so it needs bending back out (just a little) before re-inserting.


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