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MG MGB Technical - HELLA HAZARD SWITCH

Hi,

Has anyone got one of these fitted?

http://www.hella.com.au/cgi-bin/catalogue.pl?flcmd=preview&flmaint=239

If so could you let me know which wire is which.

I think I can guess L & R, what are the other 3 wires labelled 54f, 15 and 49s

A search of WWW to no avail :-(

Frank
Frank Amey

No, but if you find out I'd be interested in how easy it was, and how much the switch was.

Cheers
Iain
I D Cameron

Frank,

The diagram shows 30, 15, 49s & 54f

I think you will find that these are standard wiring numbers and 30 & 15 are -ve and +ve respectively.

49s supplies power to the normal flasher unit and is disconnected on pulling the hazard switch.

54f also flashes power so presumeably could be used to trigger something else.
Chris at Octarine Services

Frank,

As I see it, judging from the diagram but not having actually seen one, it should be wired as follows:

30 - Connect to any convenient purple wire ("alway on" power to the switch)

R - connect to any convenient green/white wire (power to the Right hand turn signals)

L - connect to any convenient green/red wire (power to the left hand turn signals)

54f - powers an optional indicating lamp. Not really needed in an MG as you already have separate indicaors for LH and RH turns. If both are flashing, you know the hazards are on. The built-in lamp in the switch will also flash.

49f & 15 - Insert into the wire from the turn signal flasher and the turn signal switch. This is usually a light green/brown wire. Cut this wire and connect one of the cut ends to 15, and the other to 49f - it doesn't matter which end goes to which pin. This disconnects the power to the turn signal switch when the hazards are on, and is VERY important! Don't skip this step!

I have another scheme for doing this, using a simple ON-OFF DPDT switch, about $5.00, and a $4.00 hazard flasher if any one is interested. e-mail me off list for a diagram. I will also draw up a schematic for this switch if any one is interested (assuming it is wired as shown), showing the entire wiring, including existing turn signal wiring.
Dan Masters

When I wrote "I will also draw up a schematic for this switch" I meant the Hella switch
Dan Masters

Many thanks for your prompt replies guys, I'll give it a go.

Chris, 30 isn't numbered on the switch but there's a spade terminal seperate and rivetted on, so I'll assume that is the earth (-ve). Thanks

Frank
Frank Amey

30 is the 12v supply, which would be -ve on a positive ground car or +ve on a negative ground car. The system will operate the same no matter what the polarity, but 30 must be connected to 12v in each case.

The 12v supply should come from its own in-line fuse connected to a brown and not to the purple circuit as its fuse may have blown e.g. if the wiring to the horns got crushed in an impact.

The convention is that 15 and 49f interrupt the 12v supply to the turn flasher (green) rather than the connection between the turn flasher and the switch, but electrically it has the same effect. As Dan says it MUST be performed or the hazards can keep the fuel pump and ignition powered under certain circumstances. There is no need to cut wires, remove the spade connector from the terminal and put a male spade on your wire from there to the hazard switch to conect to the wire you have just pulled off, and a standard female spade on the wire that comes back again.

It doesn't need a ground because the in-built tell-tale will flash in anti-phase to the flashers, effectively being connected in series with them when the flasher contact is open. The relatively low wattage and high resistance of the tell-tale in series with the turn bulbs means it will glow at almost full brightness while they won't glow at all. When the flasher contact closesd again it shorts out the tell-tale dimming it and supplying a full 12v to the turn bulbs, so lighting them.
Paul Hunt

This thread was discussed between 20/01/2004 and 21/01/2004

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